{"id":91120,"date":"2026-08-07T00:08:46","date_gmt":"2026-08-06T16:08:46","guid":{"rendered":"https:\/\/www.wsisp.com\/helps\/91120.html"},"modified":"2026-08-07T00:08:46","modified_gmt":"2026-08-06T16:08:46","slug":"%e3%80%90%e4%bd%a0%e4%b8%8d%e7%9f%a5%e9%81%93%e7%9a%84javascript%e3%80%91%e6%b7%b1%e5%85%a5%e7%90%86%e8%a7%a3-javascript-%e5%af%b9%e8%b1%a1%ef%bc%9a%e5%b1%9e%e6%80%a7%e3%80%81%e6%8f%8f%e8%bf%b0","status":"publish","type":"post","link":"https:\/\/www.wsisp.com\/helps\/91120.html","title":{"rendered":"\u3010\u4f60\u4e0d\u77e5\u9053\u7684javascript\u3011\u6df1\u5165\u7406\u89e3 JavaScript \u5bf9\u8c61\uff1a\u5c5e\u6027\u3001\u63cf\u8ff0\u7b26\u3001\u4e0d\u53ef\u53d8\u6027\u4e0e\u8fed\u4ee3\u673a"},"content":{"rendered":"<\/p>\n<h4>\u6df1\u5165\u7406\u89e3 JavaScript \u5bf9\u8c61&#xff1a;\u5c5e\u6027\u3001\u63cf\u8ff0\u7b26\u3001\u4e0d\u53ef\u53d8\u6027\u4e0e\u8fed\u4ee3\u673a\u5236<\/h4>\n<ul>\n<li>\u524d\u8a00<\/li>\n<li>1. \u5bf9\u8c61\u7684\u8bed\u6cd5\u4e0e\u7c7b\u578b\u57fa\u7840<\/li>\n<li>\n<ul>\n<li>1.1 \u5b57\u9762\u91cf\u5f62\u5f0f\u4e0e\u6784\u9020\u5f62\u5f0f<\/li>\n<li>1.2 \u57fa\u672c\u7c7b\u578b\u3001\u5bf9\u8c61\u5b50\u7c7b\u578b\u4e0e\u5185\u7f6e\u5bf9\u8c61<\/li>\n<\/ul>\n<\/li>\n<li>2. \u5c5e\u6027\u5185\u5bb9\u4e0e\u8bbf\u95ee\u673a\u5236<\/li>\n<li>\n<ul>\n<li>2.1 \u5c5e\u6027\u8bbf\u95ee\u4e0e\u5c5e\u6027\u540d\u8f6c\u6362<\/li>\n<li>2.2 \u53ef\u8ba1\u7b97\u5c5e\u6027\u540d\u4e0e Symbol<\/li>\n<li>2.3 \u51fd\u6570\u5c5e\u6027\u3001\u6570\u7ec4\u5c5e\u6027\u4e0e\u201c\u65b9\u6cd5\u201d\u6982\u5ff5<\/li>\n<\/ul>\n<\/li>\n<li>3. \u5bf9\u8c61\u590d\u5236\u4e0e\u5c5e\u6027\u63cf\u8ff0\u7b26<\/li>\n<li>\n<ul>\n<li>3.1 \u6d45\u590d\u5236\u3001\u6df1\u590d\u5236\u4e0e\u5faa\u73af\u5f15\u7528<\/li>\n<li>3.2 \u63cf\u8ff0\u5c5e\u6027\u884c\u4e3a\u7684\u56db\u4e2a\u7279\u6027<\/li>\n<\/ul>\n<\/li>\n<li>4. \u63a7\u5236\u5bf9\u8c61\u7684\u53ef\u53d8\u7a0b\u5ea6<\/li>\n<li>\n<ul>\n<li>4.1 \u5bf9\u8c61\u5e38\u91cf\u4e0e\u7981\u6b62\u6269\u5c55<\/li>\n<li>4.2 &#096;seal()&#096;\u3001&#096;freeze()&#096; \u4e0e\u6d45\u4e0d\u53ef\u53d8\u6027<\/li>\n<\/ul>\n<\/li>\n<li>5. \u5c5e\u6027\u8bfb\u5199\u7684\u5185\u90e8\u8fc7\u7a0b<\/li>\n<li>\n<ul>\n<li>5.1 &#096;[[Get]]&#096;&#xff1a;\u8bfb\u53d6\u4e0d\u53ea\u662f\u4e00\u6b21\u67e5\u8868<\/li>\n<li>5.2 &#096;[[Put]]&#096;&#xff1a;\u8d4b\u503c\u524d\u5148\u68c0\u67e5\u5c5e\u6027\u89c4\u5219<\/li>\n<li>5.3 Getter \u4e0e Setter<\/li>\n<\/ul>\n<\/li>\n<li>6. \u5c5e\u6027\u5b58\u5728\u6027\u4e0e\u53ef\u679a\u4e3e\u6027<\/li>\n<li>\n<ul>\n<li>6.1 &#096;in&#096; \u4e0e\u81ea\u6709\u5c5e\u6027\u68c0\u67e5<\/li>\n<li>6.2 \u679a\u4e3e\u3001\u5c5e\u6027\u540d\u5217\u8868\u4e0e\u68c0\u67e5\u8fb9\u754c<\/li>\n<\/ul>\n<\/li>\n<li>7. \u904d\u5386\u4e0e\u8fed\u4ee3\u534f\u8bae<\/li>\n<li>\n<ul>\n<li>7.1 \u679a\u4e3e\u5c5e\u6027\u4e0e\u8fed\u4ee3\u503c<\/li>\n<li>7.2 \u8fed\u4ee3\u5668\u534f\u8bae\u4e0e\u81ea\u5b9a\u4e49\u8fed\u4ee3\u5668<\/li>\n<\/ul>\n<\/li>\n<li>\u603b\u7ed3<\/li>\n<\/ul>\n<h2>\u524d\u8a00<\/h2>\n<p>\u5bf9\u8c61\u51e0\u4e4e\u8d2f\u7a7f\u4e86\u6240\u6709 JavaScript \u7a0b\u5e8f&#xff1a;\u914d\u7f6e\u9879\u7528\u5bf9\u8c61\u7ec4\u7ec7&#xff0c;\u6570\u7ec4\u548c\u51fd\u6570\u672c\u8eab\u4e5f\u662f\u7279\u6b8a\u5bf9\u8c61&#xff0c;\u539f\u578b\u94fe\u5efa\u7acb\u5728\u5bf9\u8c61\u4e4b\u95f4&#xff0c;\u7c7b\u6700\u7ec8\u4ecd\u8981\u843d\u5b9e\u4e3a\u5bf9\u8c61\u4e0e\u539f\u578b\u7684\u534f\u4f5c\u3002\u7136\u800c&#xff0c;\u201c\u4f1a\u5199\u5bf9\u8c61\u5b57\u9762\u91cf\u201d\u548c\u201c\u771f\u6b63\u7406\u89e3\u5bf9\u8c61\u201d\u5e76\u4e0d\u662f\u4e00\u56de\u4e8b\u3002\u5c5e\u6027\u540d\u4e3a\u4ec0\u4e48\u603b\u80fd\u5199\u6210\u5b57\u7b26\u4e32&#xff1f;\u6570\u7ec4\u6dfb\u52a0\u67d0\u4e9b\u5c5e\u6027\u65f6\u4e3a\u4ec0\u4e48\u4f1a\u6539\u53d8 length&#xff1f;\u53ea\u5b9a\u4e49 getter \u7684\u5c5e\u6027\u4e3a\u4ec0\u4e48\u65e0\u6cd5\u8d4b\u503c&#xff1f;Object.freeze() \u4e3a\u4ec0\u4e48\u51bb\u4e0d\u4f4f\u5d4c\u5957\u5bf9\u8c61&#xff1f;\u8fd9\u4e9b\u95ee\u9898\u90fd\u6307\u5411\u540c\u4e00\u4e2a\u6838\u5fc3&#xff1a;\u5bf9\u8c61\u4e0d\u662f\u4e00\u7ec4\u677e\u6563\u7684\u952e\u503c\u5bf9&#xff0c;\u800c\u662f\u4e00\u5957\u7531\u5c5e\u6027\u63cf\u8ff0\u7b26\u3001\u5185\u90e8\u64cd\u4f5c\u548c\u8fed\u4ee3\u534f\u8bae\u5171\u540c\u652f\u6491\u7684\u8bed\u8a00\u673a\u5236\u3002<\/p>\n<p>\u672c\u6587\u4ece\u5bf9\u8c61\u7684\u521b\u5efa\u8bed\u6cd5\u51fa\u53d1&#xff0c;\u4f9d\u6b21\u8bb2\u6e05\u7c7b\u578b\u4e0e\u5185\u7f6e\u5bf9\u8c61\u3001\u5c5e\u6027\u8bbf\u95ee\u3001\u53ef\u8ba1\u7b97\u5c5e\u6027\u540d\u3001\u51fd\u6570\u5c5e\u6027\u3001\u6570\u7ec4\u3001\u5bf9\u8c61\u590d\u5236\u3001\u5c5e\u6027\u63cf\u8ff0\u7b26\u3001\u4e0d\u53ef\u53d8\u6027\u3001\u5185\u90e8 [[Get]] \u4e0e [[Put]]\u3001Getter\/Setter\u3001\u5c5e\u6027\u5b58\u5728\u6027\u4ee5\u53ca\u904d\u5386\u534f\u8bae\u3002\u6bcf\u6bb5\u793a\u4f8b\u90fd\u4f1a\u7ed3\u5408\u6267\u884c\u8fc7\u7a0b\u8bf4\u660e\u7ed3\u679c\u4ea7\u751f\u7684\u539f\u56e0&#xff0c;\u5e2e\u52a9\u8bfb\u8005\u4ece\u201c\u8bb0\u4f4f API\u201d\u8d70\u5411\u201c\u7406\u89e3\u89c4\u5219\u201d\u3002<\/p>\n<p>\u6838\u5fc3\u8ba4\u8bc6&#xff1a;JavaScript \u5bf9\u8c61\u4fdd\u5b58\u7684\u662f\u5c5e\u6027&#xff1b;\u5c5e\u6027\u540d\u7528\u4e8e\u5b9a\u4f4d\u5c5e\u6027&#xff0c;\u5c5e\u6027\u63cf\u8ff0\u7b26\u51b3\u5b9a\u5c5e\u6027\u600e\u6837\u8868\u73b0&#xff0c;\u5c5e\u6027\u503c\u5219\u65e2\u53ef\u4ee5\u662f\u666e\u901a\u503c&#xff0c;\u4e5f\u53ef\u4ee5\u662f\u5bf9\u53e6\u4e00\u4e2a\u5bf9\u8c61\u6216\u51fd\u6570\u7684\u5f15\u7528\u3002<\/p>\n<h2>1. \u5bf9\u8c61\u7684\u8bed\u6cd5\u4e0e\u7c7b\u578b\u57fa\u7840<\/h2>\n<h3>1.1 \u5b57\u9762\u91cf\u5f62\u5f0f\u4e0e\u6784\u9020\u5f62\u5f0f<\/h3>\n<p>JavaScript \u5b9a\u4e49\u5bf9\u8c61\u6709\u4e24\u79cd\u57fa\u672c\u65b9\u5f0f\u3002\u6700\u5e38\u7528\u7684\u662f\u5bf9\u8c61\u5b57\u9762\u91cf&#xff0c;\u5b83\u5141\u8bb8\u5728\u521b\u5efa\u5bf9\u8c61\u7684\u540c\u65f6\u76f4\u63a5\u5199\u5165\u591a\u4e2a\u5c5e\u6027&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObj <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">key<\/span><span class=\"token operator\">:<\/span> value<br \/>\n    <span class=\"token comment\">\/\/ &#8230;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>\u53e6\u4e00\u79cd\u662f\u6784\u9020\u5f62\u5f0f&#xff0c;\u5148\u901a\u8fc7 new Object() \u521b\u5efa\u7a7a\u5bf9\u8c61&#xff0c;\u518d\u9010\u4e2a\u6dfb\u52a0\u5c5e\u6027&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObj <span class=\"token operator\">&#061;<\/span> <span class=\"token keyword\">new<\/span> <span class=\"token class-name\">Object<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\nmyObj<span class=\"token punctuation\">.<\/span>key <span class=\"token operator\">&#061;<\/span> value<span class=\"token punctuation\">;<\/span><\/p>\n<p>\u8fd9\u4e24\u79cd\u5f62\u5f0f\u6700\u540e\u90fd\u5f97\u5230\u5bf9\u8c61&#xff0c;\u4e3b\u8981\u533a\u522b\u5728\u4e8e\u8868\u8fbe\u65b9\u5f0f\u3002\u5b57\u9762\u91cf\u53ef\u4ee5\u5728\u521b\u5efa\u9636\u6bb5\u4e00\u6b21\u58f0\u660e\u591a\u4e2a\u952e\u503c\u5bf9&#xff0c;\u7ed3\u6784\u7d27\u51d1\u3001\u53ef\u8bfb\u6027\u597d&#xff1b;\u6784\u9020\u5f62\u5f0f\u901a\u5e38\u9700\u8981\u540e\u7eed\u9010\u9879\u8d4b\u503c\u3002\u5728\u6ca1\u6709\u7279\u6b8a\u517c\u5bb9\u9700\u6c42\u65f6&#xff0c;\u5e94\u4f18\u5148\u4f7f\u7528\u5bf9\u8c61\u5b57\u9762\u91cf\u3002<\/p>\n<table>\n<tr>\u5bf9\u6bd4\u9879\u5bf9\u8c61\u5b57\u9762\u91cf\u6784\u9020\u5f62\u5f0f<\/tr>\n<tbody>\n<tr>\n<td>\u5178\u578b\u5199\u6cd5<\/td>\n<td>{ key: value }<\/td>\n<td>new Object()<\/td>\n<\/tr>\n<tr>\n<td>\u521b\u5efa\u65f6\u6dfb\u52a0\u5c5e\u6027<\/td>\n<td>\u53ef\u4ee5\u4e00\u6b21\u6dfb\u52a0\u591a\u4e2a<\/td>\n<td>\u901a\u5e38\u521b\u5efa\u540e\u9010\u4e2a\u6dfb\u52a0<\/td>\n<\/tr>\n<tr>\n<td>\u53ef\u8bfb\u6027<\/td>\n<td>\u7ed3\u6784\u76f4\u89c2<\/td>\n<td>\u4ee3\u7801\u76f8\u5bf9\u5197\u957f<\/td>\n<\/tr>\n<tr>\n<td>\u5e38\u89c1\u4f7f\u7528\u573a\u666f<\/td>\n<td>\u7edd\u5927\u591a\u6570\u666e\u901a\u5bf9\u8c61<\/td>\n<td>\u5c11\u6570\u52a8\u6001\u6784\u9020\u6216\u6559\u5b66\u573a\u666f<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>\u5bf9\u8c61\u5b57\u9762\u91cf\u4e2d\u7684\u201c\u6587\u5b57\u58f0\u660e\u201d\u5e76\u4e0d\u610f\u5473\u7740\u5185\u90e8\u53ea\u6709\u7b80\u5355\u6587\u672c\u3002\u5c5e\u6027\u503c\u53ef\u4ee5\u662f\u6570\u5b57\u3001\u5b57\u7b26\u4e32\u3001\u6570\u7ec4\u3001\u51fd\u6570&#xff0c;\u4e5f\u53ef\u4ee5\u7ee7\u7eed\u6307\u5411\u5176\u4ed6\u5bf9\u8c61&#xff0c;\u7531\u6b64\u5f62\u6210\u590d\u6742\u7684\u6570\u636e\u7ed3\u6784\u3002<\/p>\n<h3>1.2 \u57fa\u672c\u7c7b\u578b\u3001\u5bf9\u8c61\u5b50\u7c7b\u578b\u4e0e\u5185\u7f6e\u5bf9\u8c61<\/h3>\n<p>\u7406\u89e3\u5bf9\u8c61\u4e4b\u524d&#xff0c;\u5fc5\u987b\u5148\u5206\u6e05 JavaScript \u7684\u4e3b\u8981\u7c7b\u578b\u3002\u4f20\u7edf\u5206\u7c7b\u4e2d\u6709\u516d\u79cd\u4e3b\u8981\u7c7b\u578b&#xff1a;<\/p>\n<ul>\n<li>string<\/li>\n<li>number<\/li>\n<li>boolean<\/li>\n<li>null<\/li>\n<li>undefined<\/li>\n<li>object<\/li>\n<\/ul>\n<p>ES6 \u53c8\u52a0\u5165\u4e86 symbol&#xff0c;\u540e\u6765\u8fd8\u52a0\u5165\u4e86 bigint\u3002\u5176\u4e2d&#xff0c;\u7b80\u5355\u57fa\u672c\u7c7b\u578b\u672c\u8eab\u5e76\u4e0d\u662f\u5bf9\u8c61\u3002null \u662f\u4e00\u4e2a\u5bb9\u6613\u5236\u9020\u8bef\u89e3\u7684\u4f8b\u5916&#xff1a;<\/p>\n<p><span class=\"token keyword\">typeof<\/span> <span class=\"token keyword\">null<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ &#034;object&#034;<\/span><\/p>\n<p>\u8fd9\u4e2a\u7ed3\u679c\u6765\u81ea JavaScript \u65e9\u671f\u5b9e\u73b0\u9057\u7559\u7684\u95ee\u9898&#xff0c;\u4e0d\u80fd\u636e\u6b64\u5224\u65ad null \u662f\u5bf9\u8c61\u3002\u4e5f\u6b63\u56e0\u4e3a\u5982\u6b64&#xff0c;\u201cJavaScript \u91cc\u4e00\u5207\u90fd\u662f\u5bf9\u8c61\u201d\u5e76\u4e0d\u51c6\u786e\u3002<\/p>\n<p>\u5bf9\u8c61\u7c7b\u578b\u5185\u90e8\u8fd8\u5305\u542b\u8bb8\u591a\u7279\u6b8a\u5b50\u7c7b\u578b\u3002\u51fd\u6570\u662f\u53ef\u8c03\u7528\u5bf9\u8c61&#xff0c;\u5185\u90e8\u5177\u6709\u8ba9\u5b83\u80fd\u591f\u88ab\u8c03\u7528\u7684 [[Call]] \u80fd\u529b&#xff1b;\u51fd\u6570\u53ef\u4ee5\u50cf\u5176\u4ed6\u503c\u4e00\u6837\u8d4b\u7ed9\u53d8\u91cf\u3001\u4f5c\u4e3a\u53c2\u6570\u4f20\u9012\u6216\u4ece\u51fd\u6570\u8fd4\u56de&#xff0c;\u56e0\u6b64\u4e5f\u5e38\u88ab\u79f0\u4e3a\u201c\u4e00\u7b49\u516c\u6c11\u201d\u3002\u6570\u7ec4\u4e5f\u662f\u5bf9\u8c61&#xff0c;\u4f46\u5b83\u4e3a\u6709\u5e8f\u3001\u6570\u503c\u7d22\u5f15\u7684\u6570\u636e\u63d0\u4f9b\u4e86\u66f4\u9002\u5408\u7684\u5b58\u50a8\u4e0e\u884c\u4e3a&#xff0c;\u4e0d\u80fd\u7b80\u5355\u7406\u89e3\u6210\u5e26\u6570\u5b57\u5c5e\u6027\u7684\u666e\u901a\u5bf9\u8c61\u3002<\/p>\n<p>JavaScript \u8fd8\u63d0\u4f9b\u4e86\u4e00\u7ec4\u5e38\u89c1\u7684\u5185\u7f6e\u5bf9\u8c61&#xff1a;<\/p>\n<table>\n<tr>\u5185\u7f6e\u5bf9\u8c61\u4e3b\u8981\u7528\u9014\u662f\u5426\u901a\u5e38\u9700\u8981\u663e\u5f0f\u6784\u9020<\/tr>\n<tbody>\n<tr>\n<td>String\u3001Number\u3001Boolean<\/td>\n<td>\u57fa\u672c\u503c\u7684\u5305\u88c5\u5bf9\u8c61<\/td>\n<td>\u901a\u5e38\u4e0d\u9700\u8981<\/td>\n<\/tr>\n<tr>\n<td>Object<\/td>\n<td>\u901a\u7528\u5bf9\u8c61<\/td>\n<td>\u4f18\u5148\u4f7f\u7528\u5b57\u9762\u91cf {}<\/td>\n<\/tr>\n<tr>\n<td>Function<\/td>\n<td>\u51fd\u6570\u5bf9\u8c61<\/td>\n<td>\u4f18\u5148\u4f7f\u7528\u51fd\u6570\u58f0\u660e\u6216\u8868\u8fbe\u5f0f<\/td>\n<\/tr>\n<tr>\n<td>Array<\/td>\n<td>\u6709\u5e8f\u96c6\u5408<\/td>\n<td>\u4f18\u5148\u4f7f\u7528\u6570\u7ec4\u5b57\u9762\u91cf []<\/td>\n<\/tr>\n<tr>\n<td>Date<\/td>\n<td>\u65e5\u671f\u4e0e\u65f6\u95f4<\/td>\n<td>\u901a\u5e38\u901a\u8fc7\u6784\u9020\u5f62\u5f0f\u521b\u5efa<\/td>\n<\/tr>\n<tr>\n<td>RegExp<\/td>\n<td>\u6b63\u5219\u8868\u8fbe\u5f0f<\/td>\n<td>\u901a\u5e38\u4f18\u5148\u4f7f\u7528\u6b63\u5219\u5b57\u9762\u91cf<\/td>\n<\/tr>\n<tr>\n<td>Error<\/td>\n<td>\u9519\u8bef\u5bf9\u8c61<\/td>\n<td>\u53ef\u7531\u8fd0\u884c\u65f6\u81ea\u52a8\u4ea7\u751f&#xff0c;\u4e5f\u53ef\u663e\u5f0f\u521b\u5efa<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>\u8fd9\u4e9b\u540d\u5b57\u770b\u8d77\u6765\u50cf\u5176\u4ed6\u8bed\u8a00\u4e2d\u7684\u201c\u7c7b\u201d&#xff0c;\u4e5f\u53ef\u4ee5\u548c new \u4e00\u8d77\u4f7f\u7528&#xff0c;\u4f46\u66f4\u51c6\u786e\u7684\u7406\u89e3\u662f&#xff1a;\u5b83\u4eec\u80fd\u591f\u521b\u5efa\u5bf9\u5e94\u7684\u5bf9\u8c61\u5b50\u7c7b\u578b\u3002\u4e0b\u9762\u6bd4\u8f83\u5b57\u7b26\u4e32\u57fa\u672c\u503c\u548c String \u5305\u88c5\u5bf9\u8c61&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> strPrimitive <span class=\"token operator\">&#061;<\/span> <span class=\"token string\">&#034;I am a string&#034;<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p><span class=\"token keyword\">typeof<\/span> strPrimitive<span class=\"token punctuation\">;<\/span>                   <span class=\"token comment\">\/\/ &#034;string&#034;<\/span><br \/>\nstrPrimitive <span class=\"token keyword\">instanceof<\/span> <span class=\"token class-name\">String<\/span><span class=\"token punctuation\">;<\/span>        <span class=\"token comment\">\/\/ false<\/span><\/p>\n<p><span class=\"token keyword\">var<\/span> strObject <span class=\"token operator\">&#061;<\/span> <span class=\"token keyword\">new<\/span> <span class=\"token class-name\">String<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;I am a string&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p><span class=\"token keyword\">typeof<\/span> strObject<span class=\"token punctuation\">;<\/span>                      <span class=\"token comment\">\/\/ &#034;object&#034;<\/span><br \/>\nstrObject <span class=\"token keyword\">instanceof<\/span> <span class=\"token class-name\">String<\/span><span class=\"token punctuation\">;<\/span>           <span class=\"token comment\">\/\/ true<\/span><\/p>\n<p><span class=\"token class-name\">Object<\/span><span class=\"token punctuation\">.<\/span>prototype<span class=\"token punctuation\">.<\/span><span class=\"token function\">toString<\/span><span class=\"token punctuation\">.<\/span><span class=\"token function\">call<\/span><span class=\"token punctuation\">(<\/span>strObject<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ &#034;[object String]&#034;<\/span><\/p>\n<p>strPrimitive \u662f\u5b57\u7b26\u4e32\u57fa\u672c\u503c&#xff0c;\u6240\u4ee5 typeof \u8fd4\u56de &#034;string&#034;&#xff0c;\u5b83\u4e5f\u4e0d\u662f String \u7684\u5b9e\u4f8b\u3002strObject \u5219\u662f\u663e\u5f0f\u6784\u9020\u51fa\u7684\u5305\u88c5\u5bf9\u8c61&#xff0c;\u56e0\u6b64\u5c5e\u4e8e\u5bf9\u8c61&#xff0c;\u5e76\u80fd\u901a\u8fc7 instanceof String \u68c0\u67e5\u3002Object.prototype.toString.call(&#8230;) \u8fdb\u4e00\u6b65\u663e\u793a\u5b83\u7684\u5185\u90e8\u54c1\u724c\u662f String\u3002<\/p>\n<p>\u57fa\u672c\u503c\u660e\u660e\u4e0d\u662f\u5bf9\u8c61&#xff0c;\u4e3a\u4ec0\u4e48\u4ecd\u80fd\u8bbf\u95ee .length \u6216\u8c03\u7528 .charAt()&#xff1f;\u539f\u56e0\u662f JavaScript \u4f1a\u5728\u9700\u8981\u65f6\u5bf9\u57fa\u672c\u503c\u8fdb\u884c\u81ea\u52a8\u88c5\u7bb1&#xff1a;\u4e34\u65f6\u628a\u5b57\u7b26\u4e32\u8f6c\u6362\u6210\u5bf9\u5e94\u7684 String \u5305\u88c5\u5bf9\u8c61&#xff0c;\u5b8c\u6210\u5c5e\u6027\u8bbf\u95ee\u540e\u518d\u4e22\u5f03\u4e34\u65f6\u5bf9\u8c61\u3002<\/p>\n<p><span class=\"token keyword\">var<\/span> strPrimitive <span class=\"token operator\">&#061;<\/span> <span class=\"token string\">&#034;I am a string&#034;<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>console<span class=\"token punctuation\">.<\/span><span class=\"token function\">log<\/span><span class=\"token punctuation\">(<\/span>strPrimitive<span class=\"token punctuation\">.<\/span>length<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span>       <span class=\"token comment\">\/\/ 13<\/span><br \/>\nconsole<span class=\"token punctuation\">.<\/span><span class=\"token function\">log<\/span><span class=\"token punctuation\">(<\/span>strPrimitive<span class=\"token punctuation\">.<\/span><span class=\"token function\">charAt<\/span><span class=\"token punctuation\">(<\/span><span class=\"token number\">3<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span>    <span class=\"token comment\">\/\/ &#034;m&#034;<\/span><\/p>\n<p>\u540c\u6837\u7684\u673a\u5236\u4e5f\u9002\u7528\u4e8e\u6570\u5b57\u548c\u5e03\u5c14\u503c&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> numberValue <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">42.359<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>console<span class=\"token punctuation\">.<\/span><span class=\"token function\">log<\/span><span class=\"token punctuation\">(<\/span>numberValue<span class=\"token punctuation\">.<\/span><span class=\"token function\">toFixed<\/span><span class=\"token punctuation\">(<\/span><span class=\"token number\">2<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ &#034;42.36&#034;<\/span><\/p>\n<p>\u56e0\u6b64&#xff0c;\u4e0d\u5e94\u8be5\u4e3a\u4e86\u8c03\u7528\u5b57\u7b26\u4e32\u3001\u6570\u5b57\u6216\u5e03\u5c14\u503c\u4e0a\u7684\u65b9\u6cd5\u800c\u624b\u52a8\u6267\u884c new String()\u3001new Number() \u6216 new Boolean()\u3002\u5305\u88c5\u5bf9\u8c61\u548c\u57fa\u672c\u503c\u5728\u7c7b\u578b\u5224\u65ad\u3001\u771f\u5047\u5224\u65ad\u53ca\u76f8\u7b49\u6bd4\u8f83\u4e0a\u90fd\u53ef\u80fd\u8868\u73b0\u4e0d\u540c&#xff0c;\u663e\u5f0f\u5305\u88c5\u53cd\u800c\u5bb9\u6613\u5f15\u5165\u95ee\u9898\u3002\u9700\u8981\u540c\u65f6\u8bb0\u4f4f\u51e0\u4e2a\u8fb9\u754c&#xff1a;null \u548c undefined \u6ca1\u6709\u5bf9\u5e94\u7684\u5305\u88c5\u6784\u9020\u5f62\u5f0f&#xff1b;Date \u6ca1\u6709\u65e5\u671f\u5b57\u9762\u91cf&#xff0c;\u53ea\u80fd\u901a\u8fc7\u6784\u9020\u65b9\u5f0f\u521b\u5efa&#xff1b;Object\u3001Array\u3001Function \u548c RegExp \u867d\u7136\u90fd\u652f\u6301\u6784\u9020\u5f62\u5f0f&#xff0c;\u4f46\u901a\u5e38\u6709\u66f4\u6e05\u6670\u7684\u5b57\u9762\u91cf\u6216\u58f0\u660e\u8bed\u6cd5\u3002<\/p>\n<h2>2. \u5c5e\u6027\u5185\u5bb9\u4e0e\u8bbf\u95ee\u673a\u5236<\/h2>\n<h3>2.1 \u5c5e\u6027\u8bbf\u95ee\u4e0e\u5c5e\u6027\u540d\u8f6c\u6362<\/h3>\n<p>\u4ece\u6982\u5ff5\u4e0a\u770b&#xff0c;\u5bf9\u8c61\u7684\u5185\u5bb9\u7531\u82e5\u5e72\u5c5e\u6027\u7ec4\u6210\u3002\u6bcf\u4e2a\u5c5e\u6027\u90fd\u6709\u4e00\u4e2a\u5c5e\u6027\u540d&#xff0c;\u5e76\u5728\u5bf9\u5e94\u4f4d\u7f6e\u4fdd\u5b58\u4e00\u4e2a\u503c\u3002\u4e3a\u4e86\u4fbf\u4e8e\u7406\u89e3&#xff0c;\u53ef\u4ee5\u628a\u5c5e\u6027\u540d\u770b\u6210\u6307\u5411\u503c\u6240\u5728\u4f4d\u7f6e\u7684\u7d22\u5f15&#xff0c;\u4f46\u5bf9\u8c61\u771f\u6b63\u7ef4\u62a4\u7684\u5e76\u4e0d\u4ec5\u662f\u540d\u79f0\u548c\u503c&#xff0c;\u540e\u9762\u8fd8\u4f1a\u770b\u5230\u6bcf\u4e2a\u5c5e\u6027\u90fd\u5e26\u6709\u81ea\u5df1\u7684\u63cf\u8ff0\u4fe1\u606f\u3002<\/p>\n<p>\u8bbf\u95ee\u5c5e\u6027\u6709\u4e24\u79cd\u8bed\u6cd5&#xff1a;\u5c5e\u6027\u8bbf\u95ee\u548c\u952e\u8bbf\u95ee\u3002<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">a<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">2<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">.<\/span>a<span class=\"token punctuation\">;<\/span>      <span class=\"token comment\">\/\/ 2<\/span><br \/>\nmyObject<span class=\"token punctuation\">[<\/span><span class=\"token string\">&#034;a&#034;<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ 2<\/span><\/p>\n<p>\u4e24\u79cd\u5199\u6cd5\u8bbf\u95ee\u7684\u662f\u540c\u4e00\u4e2a\u5c5e\u6027&#xff0c;\u533a\u522b\u5728\u4e8e\u5bf9\u5c5e\u6027\u540d\u7684\u8981\u6c42\u3002\u70b9\u8bed\u6cd5\u540e\u7684\u540d\u79f0\u5fc5\u987b\u6ee1\u8db3\u6807\u8bc6\u7b26\u89c4\u5219&#xff0c;\u800c\u65b9\u62ec\u53f7\u53ef\u4ee5\u63a5\u6536\u4efb\u610f\u80fd\u591f\u8ba1\u7b97\u51fa\u5c5e\u6027\u952e\u7684\u8868\u8fbe\u5f0f&#xff0c;\u56e0\u6b64\u66f4\u7075\u6d3b&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">[<\/span><span class=\"token string\">&#034;Super-Fun!&#034;<\/span><span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> <span class=\"token string\">&#034;hello&#034;<\/span><span class=\"token punctuation\">;<\/span><br \/>\nconsole<span class=\"token punctuation\">.<\/span><span class=\"token function\">log<\/span><span class=\"token punctuation\">(<\/span>myObject<span class=\"token punctuation\">[<\/span><span class=\"token string\">&#034;Super-Fun!&#034;<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ &#034;hello&#034;<\/span><\/p>\n<p>Super-Fun! \u4e0d\u662f\u5408\u6cd5\u6807\u8bc6\u7b26&#xff0c;\u4e0d\u80fd\u5199\u6210 myObject.Super-Fun!&#xff0c;\u5374\u53ef\u4ee5\u4f5c\u4e3a\u5b57\u7b26\u4e32\u5c5e\u6027\u540d\u4ea4\u7ed9\u65b9\u62ec\u53f7\u3002\u5c5e\u6027\u952e\u7684\u5e95\u5c42\u7c7b\u578b\u662f\u5b57\u7b26\u4e32\u6216 Symbol&#xff1b;\u5728\u4f20\u7edf\u7684\u5b57\u7b26\u4e32\u5c5e\u6027\u540d\u573a\u666f\u4e2d&#xff0c;\u5982\u679c\u4f20\u5165\u5176\u4ed6\u7c7b\u578b\u7684\u503c&#xff0c;\u5f15\u64ce\u4f1a\u5148\u628a\u5b83\u8f6c\u6362\u6210\u5b57\u7b26\u4e32&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">[<\/span><span class=\"token boolean\">true<\/span><span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> <span class=\"token string\">&#034;foo&#034;<\/span><span class=\"token punctuation\">;<\/span><br \/>\nmyObject<span class=\"token punctuation\">[<\/span><span class=\"token number\">3<\/span><span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> <span class=\"token string\">&#034;bar&#034;<\/span><span class=\"token punctuation\">;<\/span><br \/>\nmyObject<span class=\"token punctuation\">[<\/span>myObject<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> <span class=\"token string\">&#034;baz&#034;<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">[<\/span><span class=\"token string\">&#034;true&#034;<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span>            <span class=\"token comment\">\/\/ &#034;foo&#034;<\/span><br \/>\nmyObject<span class=\"token punctuation\">[<\/span><span class=\"token string\">&#034;3&#034;<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span>               <span class=\"token comment\">\/\/ &#034;bar&#034;<\/span><br \/>\nmyObject<span class=\"token punctuation\">[<\/span><span class=\"token string\">&#034;[object Object]&#034;<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ &#034;baz&#034;<\/span><\/p>\n<p>\u6267\u884c\u7b2c\u4e00\u884c\u8d4b\u503c\u65f6&#xff0c;\u5e03\u5c14\u503c true \u53d8\u6210\u5b57\u7b26\u4e32 &#034;true&#034;&#xff1b;\u6570\u5b57 3 \u53d8\u6210 &#034;3&#034;&#xff1b;\u666e\u901a\u5bf9\u8c61\u9ed8\u8ba4\u6267\u884c\u5b57\u7b26\u4e32\u8f6c\u6362\u540e\u5f97\u5230 &#034;[object Object]&#034;\u3002\u8fd9\u4e5f\u89e3\u91ca\u4e86\u4e3a\u4ec0\u4e48\u76f4\u63a5\u62ff\u666e\u901a\u5bf9\u8c61\u5f53\u5c5e\u6027\u952e\u5f88\u5371\u9669&#xff1a;\u4e0d\u540c\u5bf9\u8c61\u53ef\u80fd\u90fd\u8f6c\u6362\u6210\u540c\u4e00\u4e2a\u5b57\u7b26\u4e32&#xff0c;\u4ece\u800c\u8986\u76d6\u540c\u4e00\u5c5e\u6027\u3002\u9700\u8981\u771f\u6b63\u4f7f\u7528\u5bf9\u8c61\u4f5c\u4e3a\u952e\u65f6&#xff0c;\u5e94\u9009\u62e9 Map&#xff1b;\u9700\u8981\u552f\u4e00\u4e14\u4e0d\u4f1a\u78b0\u649e\u7684\u5bf9\u8c61\u5c5e\u6027\u952e\u65f6&#xff0c;\u53ef\u4ee5\u9009\u62e9 Symbol\u3002<\/p>\n<p>\u6570\u7ec4\u4e5f\u9075\u5b88\u5bf9\u8c61\u7684\u5c5e\u6027\u89c4\u5219&#xff0c;\u4f46\u5b83\u4f1a\u7279\u6b8a\u5904\u7406\u7b26\u5408\u6570\u7ec4\u7d22\u5f15\u683c\u5f0f\u7684\u5c5e\u6027\u540d&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myArray <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">[<\/span><span class=\"token string\">&#034;foo&#034;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">42<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;bar&#034;<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myArray<span class=\"token punctuation\">[<\/span><span class=\"token string\">&#034;3&#034;<\/span><span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> <span class=\"token string\">&#034;baz&#034;<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myArray<span class=\"token punctuation\">.<\/span>length<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ 4<\/span><br \/>\nmyArray<span class=\"token punctuation\">[<\/span><span class=\"token number\">3<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span>     <span class=\"token comment\">\/\/ &#034;baz&#034;<\/span><\/p>\n<p>\u5b57\u7b26\u4e32 &#034;3&#034; \u4f1a\u88ab\u8bc6\u522b\u4e3a\u6709\u6548\u6570\u7ec4\u7d22\u5f15&#xff0c;\u56e0\u6b64\u8d4b\u503c\u4f4d\u7f6e\u662f\u7b2c 4 \u4e2a\u5143\u7d20&#xff0c;\u5e76\u628a length \u66f4\u65b0\u4e3a 4\u3002\u5982\u679c\u5b57\u7b26\u4e32\u4e0d\u662f\u5408\u89c4\u7684\u975e\u8d1f\u6574\u6570\u7d22\u5f15&#xff0c;\u5b83\u5c31\u53ea\u4f1a\u6210\u4e3a\u666e\u901a\u5bf9\u8c61\u5c5e\u6027&#xff0c;\u4e0d\u4f1a\u6539\u53d8\u6570\u7ec4\u957f\u5ea6\u3002<\/p>\n<h3>2.2 \u53ef\u8ba1\u7b97\u5c5e\u6027\u540d\u4e0e Symbol<\/h3>\n<p>\u65b9\u62ec\u53f7\u4e0d\u53ea\u80fd\u7528\u4e8e\u8bbf\u95ee\u5bf9\u8c61&#xff0c;\u4e5f\u80fd\u51fa\u73b0\u5728\u5bf9\u8c61\u5b57\u9762\u91cf\u4e2d\u3002ES6 \u7684\u53ef\u8ba1\u7b97\u5c5e\u6027\u540d\u5141\u8bb8\u5728\u521b\u5efa\u5bf9\u8c61\u65f6\u6267\u884c\u8868\u8fbe\u5f0f&#xff0c;\u518d\u628a\u8868\u8fbe\u5f0f\u7ed3\u679c\u4f5c\u4e3a\u5c5e\u6027\u952e&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> prefix <span class=\"token operator\">&#061;<\/span> <span class=\"token string\">&#034;foo&#034;<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token punctuation\">[<\/span>prefix <span class=\"token operator\">&#043;<\/span> <span class=\"token string\">&#034;bar&#034;<\/span><span class=\"token punctuation\">]<\/span><span class=\"token operator\">:<\/span> <span class=\"token string\">&#034;hello&#034;<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token punctuation\">[<\/span>prefix <span class=\"token operator\">&#043;<\/span> <span class=\"token string\">&#034;baz&#034;<\/span><span class=\"token punctuation\">]<\/span><span class=\"token operator\">:<\/span> <span class=\"token string\">&#034;world&#034;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">[<\/span><span class=\"token string\">&#034;foobar&#034;<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ &#034;hello&#034;<\/span><br \/>\nmyObject<span class=\"token punctuation\">[<\/span><span class=\"token string\">&#034;foobaz&#034;<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ &#034;world&#034;<\/span><\/p>\n<p>\u5bf9\u8c61\u521b\u5efa\u65f6&#xff0c;prefix &#043; &#034;bar&#034; \u548c prefix &#043; &#034;baz&#034; \u5206\u522b\u8ba1\u7b97\u4e3a &#034;foobar&#034;\u3001&#034;foobaz&#034;&#xff0c;\u56e0\u6b64\u8fd9\u4e24\u4e2a\u7ed3\u679c\u76f4\u63a5\u6210\u4e3a\u5c5e\u6027\u540d\u3002\u5b83\u975e\u5e38\u9002\u5408\u5904\u7406\u52a8\u6001\u5b57\u6bb5&#xff0c;\u4e5f\u9002\u5408\u628a Symbol \u653e\u5165\u5bf9\u8c61\u5b57\u9762\u91cf&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token punctuation\">[<\/span>Symbol<span class=\"token punctuation\">.<\/span>toStringTag<span class=\"token punctuation\">]<\/span><span class=\"token operator\">:<\/span> <span class=\"token string\">&#034;MyObject&#034;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>Symbol 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\u51fd\u6570\u5c5e\u6027\u3001\u6570\u7ec4\u5c5e\u6027\u4e0e\u201c\u65b9\u6cd5\u201d\u6982\u5ff5<\/h3>\n<p>\u5f53\u5bf9\u8c61\u5c5e\u6027\u5f15\u7528\u4e00\u4e2a\u51fd\u6570\u65f6&#xff0c;\u4eba\u4eec\u4e60\u60ef\u628a\u5b83\u79f0\u4e3a\u201c\u65b9\u6cd5\u201d\u3002\u8fd9\u79cd\u8bf4\u6cd5\u5728\u63cf\u8ff0\u8c03\u7528\u65b9\u5f0f\u65f6\u5f88\u65b9\u4fbf&#xff0c;\u4f46\u4e0d\u80fd\u56e0\u6b64\u8ba4\u4e3a\u5bf9\u8c61\u62e5\u6709\u4e00\u4e2a\u4e0e\u5916\u754c\u9694\u79bb\u7684\u51fd\u6570\u526f\u672c\u3002\u5c5e\u6027\u91cc\u4fdd\u5b58\u7684\u4f9d\u7136\u53ea\u662f\u51fd\u6570\u5bf9\u8c61\u7684\u5f15\u7528&#xff1a;<\/p>\n<p><span class=\"token keyword\">function<\/span> <span class=\"token function\">foo<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    console<span class=\"token punctuation\">.<\/span><span class=\"token function\">log<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;foo&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n<p><span class=\"token keyword\">var<\/span> someFoo <span class=\"token operator\">&#061;<\/span> foo<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ \u5bf9 foo \u7684\u53d8\u91cf\u5f15\u7528<\/span><\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">someFoo<\/span><span class=\"token operator\">:<\/span> foo<br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>foo<span class=\"token punctuation\">;<\/span>              <span class=\"token comment\">\/\/ function foo(){&#8230;}<\/span><br \/>\nsomeFoo<span class=\"token punctuation\">;<\/span>          <span class=\"token comment\">\/\/ function foo(){&#8230;}<\/span><br \/>\nmyObject<span class=\"token punctuation\">.<\/span>someFoo<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ function foo(){&#8230;}<\/span><\/p>\n<p>foo\u3001someFoo \u4e0e myObject.someFoo \u90fd\u6307\u5411\u540c\u4e00\u4e2a\u51fd\u6570\u5bf9\u8c61\u3002\u5bf9\u8c61\u6ca1\u6709\u628a\u51fd\u6570\u590d\u5236\u8fdb\u53bb&#xff0c;\u4e5f\u4e0d\u4f1a\u4ece\u5b9a\u4e49\u90a3\u4e00\u523b\u8d77\u6c38\u4e45\u62e5\u6709\u5b83\u3002\u5373\u4f7f\u51fd\u6570\u76f4\u63a5\u5199\u5728\u5bf9\u8c61\u5b57\u9762\u91cf\u4e2d&#xff0c;\u53d6\u51fa\u540e\u4ecd\u7136\u53ea\u662f\u4e00\u4e2a\u666e\u901a\u51fd\u6570\u5f15\u7528&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token function-variable function\">foo<\/span><span class=\"token operator\">:<\/span> <span class=\"token keyword\">function<\/span> <span class=\"token function\">foo<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        console<span class=\"token punctuation\">.<\/span><span class=\"token function\">log<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;foo&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p><span class=\"token keyword\">var<\/span> someFoo <span class=\"token operator\">&#061;<\/span> myObject<span class=\"token punctuation\">.<\/span>foo<span class=\"token punctuation\">;<\/span><\/p>\n<p>someFoo<span class=\"token punctuation\">;<\/span>      <span class=\"token comment\">\/\/ function foo(){&#8230;}<\/span><br \/>\nmyObject<span class=\"token punctuation\">.<\/span>foo<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ function foo(){&#8230;}<\/span><\/p>\n<p>\u771f\u6b63\u8ba9\u4e00\u6b21\u51fd\u6570\u8c03\u7528\u8868\u73b0\u5f97\u50cf\u201c\u5bf9\u8c61\u65b9\u6cd5\u201d\u7684&#xff0c;\u662f\u8c03\u7528\u4f4d\u7f6e\u3002\u4f8b\u5982 myObject.foo() \u4f1a\u8ba9\u666e\u901a\u51fd\u6570\u4f9d\u636e\u8c03\u7528\u5f62\u5f0f\u83b7\u5f97\u76f8\u5e94\u7684 this&#xff1b;\u628a\u5f15\u7528\u53d6\u51fa\u540e\u6267\u884c someFoo()&#xff0c;\u8c03\u7528\u4f4d\u7f6e\u5df2\u7ecf\u6539\u53d8&#xff0c;this \u7ed1\u5b9a\u4e5f\u53ef\u80fd\u968f\u4e4b\u53d8\u5316\u3002\u56e0\u6b64&#xff0c;\u66f4\u4e25\u8c28\u7684\u8868\u8ff0\u662f&#xff1a;\u5bf9\u8c61\u5c5e\u6027\u5f15\u7528\u4e86\u51fd\u6570&#xff0c;\u51fd\u6570\u5728\u7279\u5b9a\u8c03\u7528\u4f4d\u7f6e\u88ab\u5f53\u4f5c\u65b9\u6cd5\u8c03\u7528\u3002<\/p>\n<p>ES6 \u7684\u7b80\u6d01\u65b9\u6cd5\u8bed\u6cd5\u8fd8\u5141\u8bb8\u5728\u5bf9\u8c61\u5b57\u9762\u91cf\u4e2d\u4f7f\u7528 super\u3002\u5728\u6d89\u53ca super \u65f6&#xff0c;\u7b80\u6d01\u65b9\u6cd5\u4f1a\u4fdd\u7559\u5185\u90e8\u7684 [[HomeObject]] \u4fe1\u606f&#xff0c;\u56e0\u800c\u4e0e\u666e\u901a\u7684 foo: function () {} \u4e0d\u518d\u5b8c\u5168\u7b49\u4ef7\u3002\u8fd9\u662f\u8bed\u6cd5\u770b\u4f3c\u76f8\u8fd1\u3001\u8bed\u8a00\u8bed\u4e49\u5374\u786e\u5b9e\u5b58\u5728\u5dee\u522b\u7684\u5c11\u6570\u573a\u666f\u3002<\/p>\n<p>\u6570\u7ec4\u540c\u6837\u53ef\u4ee5\u6dfb\u52a0\u666e\u901a\u5c5e\u6027&#xff0c;\u800c\u4e14\u666e\u901a\u5c5e\u6027\u4e0d\u4f1a\u81ea\u52a8\u5f71\u54cd length&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myArray <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">[<\/span><span class=\"token string\">&#034;foo&#034;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">42<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;bar&#034;<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myArray<span class=\"token punctuation\">.<\/span>baz <span class=\"token operator\">&#061;<\/span> <span class=\"token string\">&#034;baz&#034;<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myArray<span class=\"token punctuation\">.<\/span>length<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ 3<\/span><br \/>\nmyArray<span class=\"token punctuation\">.<\/span>baz<span class=\"token punctuation\">;<\/span>    <span class=\"token comment\">\/\/ &#034;baz&#034;<\/span><\/p>\n<p>\u6570\u7ec4\u7684 length \u53ea\u8ffd\u8e2a\u6570\u7ec4\u7d22\u5f15\u8303\u56f4\u3002baz \u662f\u666e\u901a\u5c5e\u6027\u540d&#xff0c;\u6240\u4ee5\u6570\u7ec4\u4ecd\u7136\u53ea\u6709\u4e09\u4e2a\u5143\u7d20\u3002\u7ed3\u5408\u524d\u9762\u7684 myArray[&#034;3&#034;] \u793a\u4f8b&#xff0c;\u53ef\u4ee5\u5f97\u5230\u4e00\u4e2a\u5b9e\u7528\u7ed3\u8bba&#xff1a;<\/p>\n<table>\n<tr>\u6dfb\u52a0\u65b9\u5f0f\u5c5e\u6027\u6027\u8d28\u662f\u5426\u5f71\u54cd length<\/tr>\n<tbody>\n<tr>\n<td>myArray.baz &#061; &#034;baz&#034;<\/td>\n<td>\u666e\u901a\u5b57\u7b26\u4e32\u5c5e\u6027<\/td>\n<td>\u5426<\/td>\n<\/tr>\n<tr>\n<td>myArray[&#034;3&#034;] &#061; &#034;baz&#034;<\/td>\n<td>\u53ef\u8bc6\u522b\u7684\u6570\u7ec4\u7d22\u5f15<\/td>\n<td>\u662f&#xff0c;\u957f\u5ea6\u53d8\u4e3a 4<\/td>\n<\/tr>\n<tr>\n<td>myArray[3] &#061; &#034;baz&#034;<\/td>\n<td>\u6570\u503c\u6570\u7ec4\u7d22\u5f15<\/td>\n<td>\u662f&#xff0c;\u957f\u5ea6\u53d8\u4e3a 4<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>3. \u5bf9\u8c61\u590d\u5236\u4e0e\u5c5e\u6027\u63cf\u8ff0\u7b26<\/h2>\n<h3>3.1 \u6d45\u590d\u5236\u3001\u6df1\u590d\u5236\u4e0e\u5faa\u73af\u5f15\u7528<\/h3>\n<p>\u590d\u5236\u5bf9\u8c61\u7684\u96be\u70b9\u4e0d\u662f\u590d\u5236\u6570\u5b57 2&#xff0c;\u800c\u662f\u51b3\u5b9a\u5982\u4f55\u5904\u7406\u5bf9\u8c61\u5185\u90e8\u7684\u5f15\u7528\u3002\u5148\u770b\u4e00\u4e2a\u540c\u65f6\u5305\u542b\u666e\u901a\u503c\u3001\u5bf9\u8c61\u3001\u6570\u7ec4\u548c\u51fd\u6570\u7684\u7ed3\u6784&#xff1a;<\/p>\n<p><span class=\"token keyword\">function<\/span> <span class=\"token function\">anotherFunction<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token comment\">\/* &#8230; *\/<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n<p><span class=\"token keyword\">var<\/span> anotherObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">c<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">true<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p><span class=\"token keyword\">var<\/span> anotherArray <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">[<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">a<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">2<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">b<\/span><span class=\"token operator\">:<\/span> anotherObject<span class=\"token punctuation\">,<\/span>  <span class=\"token comment\">\/\/ \u5f15\u7528&#xff0c;\u4e0d\u662f\u590d\u672c<\/span><br \/>\n    <span class=\"token literal-property property\">c<\/span><span class=\"token operator\">:<\/span> anotherArray<span class=\"token punctuation\">,<\/span>   <span class=\"token comment\">\/\/ \u53e6\u4e00\u4e2a\u5f15\u7528<\/span><br \/>\n    <span class=\"token literal-property property\">d<\/span><span class=\"token operator\">:<\/span> anotherFunction<br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>anotherArray<span class=\"token punctuation\">.<\/span><span class=\"token function\">push<\/span><span class=\"token punctuation\">(<\/span>anotherObject<span class=\"token punctuation\">,<\/span> myObject<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>\u5982\u679c\u8fdb\u884c\u6d45\u590d\u5236&#xff0c;\u65b0\u5bf9\u8c61\u7684 a \u53ef\u4ee5\u76f4\u63a5\u5f97\u5230\u503c 2&#xff0c;\u4f46 b\u3001c\u3001d \u53ea\u4f1a\u590d\u5236\u5f15\u7528&#xff1a;\u65b0\u65e7\u5bf9\u8c61\u4ecd\u7136\u5171\u4eab anotherObject\u3001anotherArray \u548c anotherFunction\u3002\u5982\u679c\u8fdb\u884c\u6df1\u590d\u5236&#xff0c;\u5219\u9700\u8981\u9012\u5f52\u590d\u5236\u88ab\u5f15\u7528\u7684\u5bf9\u8c61\u4e0e\u6570\u7ec4&#xff1b;\u53ef\u8fd9\u91cc\u7684 anotherArray \u53c8\u6307\u56de\u4e86 myObject&#xff0c;\u5f62\u6210\u5faa\u73af\u5f15\u7528\u3002\u6ca1\u6709\u5faa\u73af\u68c0\u6d4b\u7684\u9012\u5f52\u590d\u5236\u4f1a\u4e0d\u65ad\u6df1\u5165&#xff0c;\u6700\u7ec8\u5bfc\u81f4\u6808\u6ea2\u51fa\u3002<\/p>\n<table>\n<tr>\u590d\u5236\u65b9\u5f0f\u7b2c\u4e00\u5c42\u666e\u901a\u503c\u5d4c\u5957\u5bf9\u8c61\/\u6570\u7ec4\u51fd\u6570\u5faa\u73af\u5f15\u7528<\/tr>\n<tbody>\n<tr>\n<td>\u6d45\u590d\u5236<\/td>\n<td>\u590d\u5236\u503c<\/td>\n<td>\u5171\u4eab\u5f15\u7528<\/td>\n<td>\u5171\u4eab\u5f15\u7528<\/td>\n<td>\u4e0d\u4f1a\u9012\u5f52&#xff0c;\u56e0\u6b64\u4e0d\u4f1a\u5361\u6b7b<\/td>\n<\/tr>\n<tr>\n<td>\u6df1\u590d\u5236<\/td>\n<td>\u590d\u5236\u503c<\/td>\n<td>\u9012\u5f52\u590d\u5236<\/td>\n<td>\u53d6\u51b3\u4e8e\u5b9e\u73b0<\/td>\n<td>\u5fc5\u987b\u663e\u5f0f\u68c0\u6d4b\u4e0e\u590d\u7528\u5df2\u590d\u5236\u5bf9\u8c61<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>\u5bf9\u4e8e\u5b8c\u5168\u7b26\u5408 JSON \u6570\u636e\u6a21\u578b\u7684\u5bf9\u8c61&#xff0c;\u53ef\u4ee5\u7528\u5e8f\u5217\u5316\u548c\u53cd\u5e8f\u5217\u5316\u5b8c\u6210\u4e00\u79cd\u6709\u9650\u7684\u6df1\u590d\u5236&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> newObj <span class=\"token operator\">&#061;<\/span> <span class=\"token constant\">JSON<\/span><span class=\"token punctuation\">.<\/span><span class=\"token function\">parse<\/span><span class=\"token punctuation\">(<\/span><span class=\"token constant\">JSON<\/span><span class=\"token punctuation\">.<\/span><span class=\"token function\">stringify<\/span><span class=\"token punctuation\">(<\/span>someObj<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>\u8fd9\u79cd\u65b9\u6cd5\u53ea\u9002\u5408 JSON \u5b89\u5168\u7684\u6570\u636e\u3002\u51fd\u6570\u3001undefined\u3001Symbol \u7b49\u5185\u5bb9\u65e0\u6cd5\u88ab\u6b63\u5e38\u4fdd\u7559&#xff0c;Date \u4f1a\u53d8\u6210\u5b57\u7b26\u4e32&#xff0c;\u5faa\u73af\u5f15\u7528\u8fd8\u4f1a\u76f4\u63a5\u629b\u9519&#xff0c;\u6240\u4ee5\u5b83\u4e0d\u662f\u901a\u7528\u6df1\u590d\u5236\u65b9\u6848\u3002<\/p>\n<p>ES6 \u7684 Object.assign() \u63d0\u4f9b\u7684\u662f\u6d45\u590d\u5236\u3002\u7b2c\u4e00\u4e2a\u53c2\u6570\u662f\u76ee\u6807\u5bf9\u8c61&#xff0c;\u540e\u7eed\u53c2\u6570\u662f\u6765\u6e90\u5bf9\u8c61&#xff1b;\u5b83\u4f1a\u628a\u6765\u6e90\u5bf9\u8c61\u7684\u81ea\u6709\u3001\u53ef\u679a\u4e3e\u5c5e\u6027\u9010\u4e2a\u8d4b\u7ed9\u76ee\u6807\u5bf9\u8c61&#xff0c;\u5e76\u8fd4\u56de\u76ee\u6807\u5bf9\u8c61&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> newObj <span class=\"token operator\">&#061;<\/span> Object<span class=\"token punctuation\">.<\/span><span class=\"token function\">assign<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">{<\/span><span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">,<\/span> myObject<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>newObj<span class=\"token punctuation\">.<\/span>a<span class=\"token punctuation\">;<\/span>                     <span class=\"token comment\">\/\/ 2<\/span><br \/>\nnewObj<span class=\"token punctuation\">.<\/span>b <span class=\"token operator\">&#061;&#061;&#061;<\/span> anotherObject<span class=\"token punctuation\">;<\/span>   <span class=\"token comment\">\/\/ true<\/span><br \/>\nnewObj<span class=\"token punctuation\">.<\/span>c <span class=\"token operator\">&#061;&#061;&#061;<\/span> anotherArray<span class=\"token punctuation\">;<\/span>    <span class=\"token comment\">\/\/ true<\/span><br \/>\nnewObj<span class=\"token punctuation\">.<\/span>d <span class=\"token operator\">&#061;&#061;&#061;<\/span> anotherFunction<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ true<\/span><\/p>\n<p>\u7ed3\u679c\u4e2d\u7684\u4e09\u4e2a true \u6e05\u695a\u8bf4\u660e&#xff1a;Object.assign() \u53ea\u590d\u5236\u4e86\u7b2c\u4e00\u5c42\u5c5e\u6027\u503c&#xff1b;\u5f53\u5c5e\u6027\u503c\u672c\u8eab\u662f\u5f15\u7528\u65f6&#xff0c;\u88ab\u590d\u5236\u7684\u4ecd\u7136\u662f\u540c\u4e00\u5f15\u7528\u3002\u9009\u62e9\u590d\u5236\u7b56\u7565\u65f6&#xff0c;\u5fc5\u987b\u5148\u660e\u786e\u4e1a\u52a1\u9700\u8981\u7684\u662f\u201c\u521b\u5efa\u4e00\u4e2a\u65b0\u7684\u5916\u58f3\u201d&#xff0c;\u8fd8\u662f\u201c\u5f97\u5230\u5b8c\u5168\u72ec\u7acb\u7684\u5bf9\u8c61\u56fe\u201d\u3002<\/p>\n<h3>3.2 \u63cf\u8ff0\u5c5e\u6027\u884c\u4e3a\u7684\u56db\u4e2a\u7279\u6027<\/h3>\n<p>\u4ece ES5 \u5f00\u59cb&#xff0c;\u53ef\u4ee5\u901a\u8fc7\u5c5e\u6027\u63cf\u8ff0\u7b26\u76f4\u63a5\u89c2\u5bdf\u548c\u63a7\u5236\u5c5e\u6027\u884c\u4e3a\u3002\u666e\u901a\u5bf9\u8c61\u5b57\u9762\u91cf\u521b\u5efa\u7684\u5c5e\u6027\u901a\u5e38\u5177\u6709\u56db\u4e2a\u7279\u6027&#xff1a;value\u3001writable\u3001enumerable \u548c configurable\u3002<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">a<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">2<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>Object<span class=\"token punctuation\">.<\/span><span class=\"token function\">getOwnPropertyDescriptor<\/span><span class=\"token punctuation\">(<\/span>myObject<span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;a&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token comment\">\/\/ {<\/span><br \/>\n<span class=\"token comment\">\/\/     value: 2,<\/span><br \/>\n<span class=\"token comment\">\/\/     writable: true,<\/span><br \/>\n<span class=\"token comment\">\/\/     enumerable: true,<\/span><br \/>\n<span class=\"token comment\">\/\/     configurable: true<\/span><br \/>\n<span class=\"token comment\">\/\/ }<\/span><\/p>\n<table>\n<tr>\u63cf\u8ff0\u7b26\u63a7\u5236\u5185\u5bb9\u666e\u901a\u5b57\u9762\u91cf\u5c5e\u6027\u7684\u9ed8\u8ba4\u72b6\u6001<\/tr>\n<tbody>\n<tr>\n<td>value<\/td>\n<td>\u5c5e\u6027\u5f53\u524d\u4fdd\u5b58\u7684\u503c<\/td>\n<td>\u521b\u5efa\u65f6\u5199\u5165\u7684\u503c<\/td>\n<\/tr>\n<tr>\n<td>writable<\/td>\n<td>\u80fd\u5426\u901a\u8fc7\u8d4b\u503c\u4fee\u6539 value<\/td>\n<td>true<\/td>\n<\/tr>\n<tr>\n<td>enumerable<\/td>\n<td>\u80fd\u5426\u51fa\u73b0\u5728\u5e38\u89c4\u679a\u4e3e\u4e2d<\/td>\n<td>true<\/td>\n<\/tr>\n<tr>\n<td>configurable<\/td>\n<td>\u80fd\u5426\u91cd\u65b0\u914d\u7f6e\u6216\u5220\u9664\u5c5e\u6027<\/td>\n<td>true<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Object.defineProperty() \u53ef\u4ee5\u521b\u5efa\u65b0\u5c5e\u6027&#xff0c;\u4e5f\u53ef\u4ee5\u4fee\u6539\u5df2\u6709\u5c5e\u6027\u7684\u63cf\u8ff0\u7b26&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>Object<span class=\"token punctuation\">.<\/span><span class=\"token function\">defineProperty<\/span><span class=\"token punctuation\">(<\/span>myObject<span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;a&#034;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">value<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">2<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">writable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">true<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">configurable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">true<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">enumerable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">true<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">.<\/span>a<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ 2<\/span><\/p>\n<p>writable \u4e3a false \u65f6&#xff0c;\u666e\u901a\u8d4b\u503c\u65e0\u6cd5\u66f4\u65b0\u5c5e\u6027\u3002\u5728\u975e\u4e25\u683c\u6a21\u5f0f\u4e0b&#xff0c;\u5931\u8d25\u901a\u5e38\u88ab\u9759\u9ed8\u5ffd\u7565&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>Object<span class=\"token punctuation\">.<\/span><span class=\"token function\">defineProperty<\/span><span class=\"token punctuation\">(<\/span>myObject<span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;a&#034;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">value<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">2<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">writable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">false<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">configurable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">true<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">enumerable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">true<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">.<\/span>a <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">3<\/span><span class=\"token punctuation\">;<\/span><br \/>\nmyObject<span class=\"token punctuation\">.<\/span>a<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ 2<\/span><\/p>\n<p>\u4e25\u683c\u6a21\u5f0f\u4e0d\u4f1a\u9759\u9ed8\u541e\u6389\u9519\u8bef&#xff0c;\u800c\u4f1a\u629b\u51fa TypeError&#xff1a;<\/p>\n<p><span class=\"token string\">&#034;use strict&#034;<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>Object<span class=\"token punctuation\">.<\/span><span class=\"token function\">defineProperty<\/span><span class=\"token punctuation\">(<\/span>myObject<span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;a&#034;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">value<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">2<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">writable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">false<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">configurable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">true<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">enumerable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">true<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">.<\/span>a <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">3<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ TypeError<\/span><\/p>\n<p>configurable \u63a7\u5236\u7684\u4e0d\u662f\u5c5e\u6027\u503c\u80fd\u5426\u4fee\u6539&#xff0c;\u800c\u662f\u63cf\u8ff0\u7b26\u80fd\u5426\u91cd\u65b0\u914d\u7f6e\u4ee5\u53ca\u5c5e\u6027\u80fd\u5426\u5220\u9664\u3002\u4e00\u65e6\u628a\u5b83\u8bbe\u4e3a false&#xff0c;\u901a\u5e38\u5c31\u4e0d\u80fd\u518d\u6062\u590d\u4e3a true&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">a<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">2<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">.<\/span>a <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">3<\/span><span class=\"token punctuation\">;<\/span><br \/>\nmyObject<span class=\"token punctuation\">.<\/span>a<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ 3<\/span><\/p>\n<p>Object<span class=\"token punctuation\">.<\/span><span class=\"token function\">defineProperty<\/span><span class=\"token punctuation\">(<\/span>myObject<span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;a&#034;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">value<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">4<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">writable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">true<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">configurable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">false<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">enumerable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">true<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">.<\/span>a<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ 4<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">.<\/span>a <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">5<\/span><span class=\"token punctuation\">;<\/span><br \/>\nmyObject<span class=\"token punctuation\">.<\/span>a<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ 5<\/span><\/p>\n<p>Object<span class=\"token punctuation\">.<\/span><span class=\"token function\">defineProperty<\/span><span class=\"token punctuation\">(<\/span>myObject<span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;a&#034;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">value<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">6<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">writable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">true<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">configurable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">true<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">enumerable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">true<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ TypeError<\/span><\/p>\n<p>\u8fd9\u91cc myObject.a &#061; 5 \u4ecd\u7136\u6210\u529f&#xff0c;\u662f\u56e0\u4e3a writable \u8fd8\u662f true&#xff1b;\u6700\u540e\u4e00\u6b21\u91cd\u65b0\u5b9a\u4e49\u5931\u8d25&#xff0c;\u5219\u662f\u56e0\u4e3a\u4ee3\u7801\u8bd5\u56fe\u628a\u4e0d\u53ef\u914d\u7f6e\u5c5e\u6027\u7684 configurable \u6539\u56de true\u3002\u5bf9\u4e0d\u53ef\u914d\u7f6e\u7684\u6570\u636e\u5c5e\u6027&#xff0c;writable \u8fd8\u5b58\u5728\u4e00\u4e2a\u5355\u5411\u4f8b\u5916&#xff1a;\u53ef\u4ee5\u4ece true \u6539\u6210 false&#xff0c;\u5374\u4e0d\u80fd\u518d\u4ece false \u6539\u56de true\u3002<\/p>\n<p>configurable: false \u8fd8\u4f1a\u8ba9 delete \u5931\u6548&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">a<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">2<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">.<\/span>a<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ 2<\/span><br \/>\n<span class=\"token keyword\">delete<\/span> myObject<span class=\"token punctuation\">.<\/span>a<span class=\"token punctuation\">;<\/span><br \/>\nmyObject<span class=\"token punctuation\">.<\/span>a<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ undefined<\/span><\/p>\n<p>Object<span class=\"token punctuation\">.<\/span><span class=\"token function\">defineProperty<\/span><span class=\"token punctuation\">(<\/span>myObject<span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;a&#034;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">value<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">2<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">writable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">true<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">configurable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">false<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">enumerable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">true<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">.<\/span>a<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ 2<\/span><br \/>\n<span class=\"token keyword\">delete<\/span> myObject<span class=\"token punctuation\">.<\/span>a<span class=\"token punctuation\">;<\/span><br \/>\nmyObject<span class=\"token punctuation\">.<\/span>a<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ 2<\/span><\/p>\n<p>\u9700\u8981\u5f3a\u8c03\u7684\u662f&#xff0c;delete myObject.a \u5220\u9664\u7684\u662f\u5bf9\u8c61\u4e0a\u7684\u5c5e\u6027\u5173\u8054&#xff0c;\u4e0d\u4f1a\u9500\u6bc1\u5c5e\u6027\u503c\u6240\u5f15\u7528\u7684\u5bf9\u8c61\u6216\u51fd\u6570\u3002JavaScript \u7684\u5185\u5b58\u56de\u6536\u53d6\u51b3\u4e8e\u4e00\u4e2a\u503c\u662f\u5426\u4ecd\u7136\u53ef\u8fbe&#xff0c;\u800c\u4e0d\u662f\u67d0\u6b21 delete \u662f\u5426\u6267\u884c\u3002<\/p>\n<p>\u6700\u540e&#xff0c;enumerable \u51b3\u5b9a\u5c5e\u6027\u662f\u5426\u53c2\u4e0e\u5e38\u89c4\u679a\u4e3e\u3002\u4e0d\u53ef\u679a\u4e3e\u5c5e\u6027\u4ecd\u7136\u5b58\u5728&#xff0c;\u4e5f\u4ecd\u7136\u53ef\u4ee5\u76f4\u63a5\u8bbf\u95ee&#xff0c;\u53ea\u662f\u4e0d\u4f1a\u51fa\u73b0\u5728 for&#8230;in\u3001Object.keys() \u7b49\u53ea\u5173\u6ce8\u53ef\u679a\u4e3e\u5c5e\u6027\u7684\u673a\u5236\u4e2d\u3002\u540e\u6587\u4f1a\u7528\u5b8c\u6574\u793a\u4f8b\u6bd4\u8f83\u8fd9\u4e9b\u68c0\u67e5\u65b9\u5f0f\u3002<\/p>\n<h2>4. \u63a7\u5236\u5bf9\u8c61\u7684\u53ef\u53d8\u7a0b\u5ea6<\/h2>\n<h3>4.1 \u5bf9\u8c61\u5e38\u91cf\u4e0e\u7981\u6b62\u6269\u5c55<\/h3>\n<p>\u5c5e\u6027\u63cf\u8ff0\u7b26\u53ef\u4ee5\u7ec4\u5408\u51fa\u4e00\u4e2a\u4e0d\u53ef\u4fee\u6539\u3001\u4e0d\u53ef\u5220\u9664\u7684\u5e38\u91cf\u5c5e\u6027&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>Object<span class=\"token punctuation\">.<\/span><span class=\"token function\">defineProperty<\/span><span class=\"token punctuation\">(<\/span>myObject<span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;FAVORITE_NUMBER&#034;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">value<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">42<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">writable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">false<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">configurable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">false<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>writable: false \u963b\u6b62\u91cd\u65b0\u8d4b\u503c&#xff0c;configurable: false \u963b\u6b62\u5220\u9664\u6216\u91cd\u65b0\u914d\u7f6e\u3002\u8fd9\u91cc\u6ca1\u6709\u663e\u5f0f\u5199 enumerable&#xff0c;\u800c Object.defineProperty() \u5bf9\u672a\u63d0\u4f9b\u7684\u5e03\u5c14\u63cf\u8ff0\u7b26\u9ed8\u8ba4\u4f7f\u7528 false&#xff0c;\u6240\u4ee5\u8fd9\u4e2a\u5e38\u91cf\u4e5f\u4e0d\u53ef\u679a\u4e3e\u3002<\/p>\n<p>\u5982\u679c\u76ee\u6807\u662f\u4e0d\u5141\u8bb8\u5bf9\u8c61\u518d\u589e\u52a0\u65b0\u5c5e\u6027&#xff0c;\u53ef\u4ee5\u4f7f\u7528 Object.preventExtensions()&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">a<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">2<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>Object<span class=\"token punctuation\">.<\/span><span class=\"token function\">preventExtensions<\/span><span class=\"token punctuation\">(<\/span>myObject<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">.<\/span>b <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">3<\/span><span class=\"token punctuation\">;<\/span><br \/>\nmyObject<span class=\"token punctuation\">.<\/span>b<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ undefined<\/span><\/p>\n<p>\u5728\u975e\u4e25\u683c\u6a21\u5f0f\u4e2d&#xff0c;\u65b0\u589e\u5c5e\u6027\u5931\u8d25\u4f46\u4e0d\u629b\u9519&#xff1b;\u4e25\u683c\u6a21\u5f0f\u4e0b\u4f1a\u629b\u51fa TypeError\u3002\u7981\u6b62\u6269\u5c55\u53ea\u963b\u6b62\u201c\u65b0\u589e\u201d&#xff0c;\u5e76\u4e0d\u4f1a\u81ea\u52a8\u628a\u5df2\u6709\u5c5e\u6027\u53d8\u6210\u53ea\u8bfb&#xff0c;\u4e5f\u4e0d\u4f1a\u81ea\u52a8\u7981\u6b62\u5220\u9664\u5df2\u6709\u5c5e\u6027\u3002<\/p>\n<h3>4.2 seal()\u3001freeze() \u4e0e\u6d45\u4e0d\u53ef\u53d8\u6027<\/h3>\n<p>JavaScript \u63d0\u4f9b\u4e86\u9010\u5c42\u589e\u5f3a\u9650\u5236\u7684\u5bf9\u8c61\u63a7\u5236\u65b9\u6cd5&#xff1a;<\/p>\n<table>\n<tr>\u64cd\u4f5c\u80fd\u5426\u65b0\u589e\u5c5e\u6027\u80fd\u5426\u5220\u9664\u5c5e\u6027\u80fd\u5426\u91cd\u65b0\u914d\u7f6e\u5c5e\u6027\u80fd\u5426\u4fee\u6539\u5df2\u6709\u6570\u636e\u5c5e\u6027\u503c<\/tr>\n<tbody>\n<tr>\n<td>\u666e\u901a\u5bf9\u8c61<\/td>\n<td>\u53ef\u4ee5<\/td>\n<td>\u53ef\u4ee5<\/td>\n<td>\u53ef\u4ee5<\/td>\n<td>\u53d6\u51b3\u4e8e writable<\/td>\n<\/tr>\n<tr>\n<td>Object.preventExtensions()<\/td>\n<td>\u4e0d\u53ef\u4ee5<\/td>\n<td>\u53ef\u4ee5<\/td>\n<td>\u53ef\u4ee5<\/td>\n<td>\u53d6\u51b3\u4e8e writable<\/td>\n<\/tr>\n<tr>\n<td>Object.seal()<\/td>\n<td>\u4e0d\u53ef\u4ee5<\/td>\n<td>\u4e0d\u53ef\u4ee5<\/td>\n<td>\u4e0d\u53ef\u4ee5<\/td>\n<td>\u539f\u5c5e\u6027\u82e5\u53ef\u5199&#xff0c;\u4ecd\u53ef\u4ee5<\/td>\n<\/tr>\n<tr>\n<td>Object.freeze()<\/td>\n<td>\u4e0d\u53ef\u4ee5<\/td>\n<td>\u4e0d\u53ef\u4ee5<\/td>\n<td>\u4e0d\u53ef\u4ee5<\/td>\n<td>\u4e0d\u53ef\u4ee5<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Object.seal() \u4f1a\u5728\u7981\u6b62\u6269\u5c55\u7684\u57fa\u7840\u4e0a&#xff0c;\u628a\u6240\u6709\u5df2\u6709\u5c5e\u6027\u6807\u8bb0\u4e3a configurable: false\u3002\u56e0\u6b64&#xff0c;\u5bc6\u5c01\u540e\u7684\u5bf9\u8c61\u4e0d\u80fd\u65b0\u589e\u3001\u5220\u9664\u6216\u91cd\u65b0\u914d\u7f6e\u5c5e\u6027&#xff0c;\u4f46\u5176\u4e2d\u539f\u672c\u53ef\u5199\u7684\u6570\u636e\u5c5e\u6027\u4ecd\u7136\u80fd\u591f\u6539\u53d8\u503c\u3002<\/p>\n<p>Object.freeze() \u4f1a\u5148\u5bc6\u5c01\u5bf9\u8c61&#xff0c;\u518d\u628a\u5df2\u6709\u6570\u636e\u5c5e\u6027\u8bbe\u4e3a writable: false\u3002\u5b83\u662f JavaScript \u5185\u7f6e\u65b9\u6cd5\u80fd\u591f\u63d0\u4f9b\u7684\u6700\u9ad8\u5c42\u7ea7\u5bf9\u8c61\u9650\u5236\u3002\u4e0d\u8fc7&#xff0c;\u8fd9\u4e9b\u64cd\u4f5c\u90fd\u53ea\u5f71\u54cd\u76ee\u6807\u5bf9\u8c61\u53ca\u5176\u76f4\u63a5\u5c5e\u6027\u63cf\u8ff0\u7b26&#xff0c;\u4e0d\u4f1a\u6cbf\u5f15\u7528\u7ee7\u7eed\u51bb\u7ed3\u5d4c\u5957\u5bf9\u8c61&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">nested<\/span><span class=\"token operator\">:<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token literal-property property\">value<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">2<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>Object<span class=\"token punctuation\">.<\/span><span class=\"token function\">freeze<\/span><span class=\"token punctuation\">(<\/span>myObject<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">.<\/span>nested<span class=\"token punctuation\">.<\/span>value <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">3<\/span><span class=\"token punctuation\">;<\/span><br \/>\nconsole<span class=\"token punctuation\">.<\/span><span class=\"token function\">log<\/span><span class=\"token punctuation\">(<\/span>myObject<span class=\"token punctuation\">.<\/span>nested<span class=\"token punctuation\">.<\/span>value<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ 3<\/span><\/p>\n<p>\u5916\u5c42\u5c5e\u6027 nested \u4fdd\u5b58\u7684\u5f15\u7528\u4e0d\u80fd\u88ab\u6362\u6210\u53e6\u4e00\u4e2a\u5bf9\u8c61&#xff0c;\u4f46\u88ab\u5f15\u7528\u5bf9\u8c61\u5185\u90e8\u7684 value \u4ecd\u53ef\u4fee\u6539\u3002\u82e5\u4e1a\u52a1\u786e\u5b9e\u9700\u8981\u201c\u6df1\u5ea6\u51bb\u7ed3\u201d&#xff0c;\u5fc5\u987b\u9012\u5f52\u904d\u5386\u6240\u6709\u5f15\u7528\u5e76\u5bf9\u6bcf\u4e2a\u5bf9\u8c61\u6267\u884c Object.freeze()&#xff0c;\u540c\u65f6\u4f7f\u7528\u96c6\u5408\u8bb0\u5f55\u5df2\u7ecf\u8bbf\u95ee\u8fc7\u7684\u5bf9\u8c61&#xff0c;\u907f\u514d\u5faa\u73af\u5f15\u7528\u5bfc\u81f4\u65e0\u9650\u9012\u5f52\u3002<\/p>\n<p>\u4e0d\u53ef\u53d8\u6027\u662f\u5206\u5c42\u7684\u3002 \u51bb\u7ed3\u4e00\u4e2a\u5bf9\u8c61&#xff0c;\u53ea\u51bb\u7ed3\u8fd9\u4e2a\u5bf9\u8c61\u81ea\u5df1\u7684\u5c5e\u6027\u8fb9\u754c&#xff1b;\u5b83\u4e0d\u4f1a\u81ea\u52a8\u51bb\u7ed3\u5c5e\u6027\u503c\u6307\u5411\u7684\u6574\u5f20\u5bf9\u8c61\u5173\u7cfb\u7f51\u3002<\/p>\n<h2>5. \u5c5e\u6027\u8bfb\u5199\u7684\u5185\u90e8\u8fc7\u7a0b<\/h2>\n<h3>5.1 [[Get]]&#xff1a;\u8bfb\u53d6\u4e0d\u53ea\u662f\u4e00\u6b21\u67e5\u8868<\/h3>\n<p>\u8868\u8fbe\u5f0f myObject.a \u770b\u8d77\u6765\u53ea\u662f\u4ece\u5bf9\u8c61\u4e2d\u53d6\u51fa\u5c5e\u6027&#xff0c;\u5b9e\u9645\u4f1a\u89e6\u53d1\u5bf9\u8c61\u5185\u90e8\u7684 [[Get]] \u64cd\u4f5c&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">a<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">2<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">.<\/span>a<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ 2<\/span><\/p>\n<p>\u5bf9\u4e8e\u666e\u901a\u5bf9\u8c61&#xff0c;[[Get]] \u9996\u5148\u68c0\u67e5\u5bf9\u8c61\u81ea\u8eab\u662f\u5426\u5b58\u5728\u540d\u4e3a a \u7684\u5c5e\u6027\u3002\u5982\u679c\u5b58\u5728&#xff0c;\u5c31\u6309\u7167\u5c5e\u6027\u7c7b\u578b\u8fd4\u56de\u503c\u6216\u6267\u884c getter&#xff1b;\u5982\u679c\u81ea\u8eab\u4e0d\u5b58\u5728&#xff0c;\u5219\u6cbf\u5185\u90e8 [[Prototype]] \u94fe\u7ee7\u7eed\u67e5\u627e\u3002\u76f4\u5230\u539f\u578b\u94fe\u672b\u7aef\u4ecd\u672a\u627e\u5230\u65f6&#xff0c;\u7ed3\u679c\u624d\u662f undefined&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">.<\/span>a<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ undefined<\/span><\/p>\n<p>\u8fd9\u5e26\u6765\u4e00\u4e2a\u91cd\u8981\u6b67\u4e49&#xff1a;\u8fd4\u56de undefined \u4e0d\u7b49\u4e8e\u5c5e\u6027\u4e0d\u5b58\u5728\u3002\u4e0b\u9762\u4e24\u4e2a\u5bf9\u8c61\u8bfb\u53d6 a \u65f6\u7ed3\u679c\u76f8\u540c&#xff0c;\u4f46\u5185\u90e8\u72b6\u6001\u5b8c\u5168\u4e0d\u540c&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> firstObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token keyword\">var<\/span> secondObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">a<\/span><span class=\"token operator\">:<\/span> <span class=\"token keyword\">undefined<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>firstObject<span class=\"token punctuation\">.<\/span>a<span class=\"token punctuation\">;<\/span>  <span class=\"token comment\">\/\/ undefined&#xff0c;\u5c5e\u6027\u4e0d\u5b58\u5728<\/span><br \/>\nsecondObject<span class=\"token punctuation\">.<\/span>a<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ undefined&#xff0c;\u5c5e\u6027\u5b58\u5728\u4f46\u503c\u5c31\u662f undefined<\/span><\/p>\n<p>\u56e0\u6b64&#xff0c;\u5224\u65ad\u5c5e\u6027\u662f\u5426\u5b58\u5728\u65f6\u4e0d\u80fd\u53ea\u770b\u8bfb\u53d6\u7ed3\u679c&#xff0c;\u5e94\u4f7f\u7528 in\u3001hasOwnProperty() \u6216 Object.hasOwn() \u7b49\u5b58\u5728\u6027\u68c0\u67e5\u3002<\/p>\n<h3>5.2 [[Put]]&#xff1a;\u8d4b\u503c\u524d\u5148\u68c0\u67e5\u5c5e\u6027\u89c4\u5219<\/h3>\n<p>\u7ed9\u5bf9\u8c61\u5c5e\u6027\u8d4b\u503c\u65f6\u4f1a\u89e6\u53d1\u5185\u90e8 [[Put]] \u64cd\u4f5c\u3002\u5bf9\u4e8e\u5df2\u7ecf\u5b58\u5728\u7684\u81ea\u6709\u5c5e\u6027&#xff0c;\u53ef\u4ee5\u628a\u4e3b\u8981\u5224\u65ad\u8fc7\u7a0b\u6982\u62ec\u4e3a&#xff1a;<\/p>\n<table>\n<tr>\u68c0\u67e5\u987a\u5e8f\u5c5e\u6027\u72b6\u6001[[Put]] \u7684\u5904\u7406<\/tr>\n<tbody>\n<tr>\n<td>1<\/td>\n<td>\u662f\u8bbf\u95ee\u63cf\u8ff0\u7b26\u5e76\u5b58\u5728 setter<\/td>\n<td>\u8c03\u7528 setter&#xff0c;\u628a\u65b0\u503c\u4f5c\u4e3a\u53c2\u6570\u4f20\u5165<\/td>\n<\/tr>\n<tr>\n<td>2<\/td>\n<td>\u662f\u6570\u636e\u63cf\u8ff0\u7b26\u4e14 writable: false<\/td>\n<td>\u975e\u4e25\u683c\u6a21\u5f0f\u9759\u9ed8\u5931\u8d25&#xff0c;\u4e25\u683c\u6a21\u5f0f\u629b\u51fa TypeError<\/td>\n<\/tr>\n<tr>\n<td>3<\/td>\n<td>\u662f\u53ef\u5199\u7684\u6570\u636e\u5c5e\u6027<\/td>\n<td>\u628a\u5c5e\u6027\u503c\u66f4\u65b0\u4e3a\u65b0\u503c<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>\u5982\u679c\u5bf9\u8c61\u81ea\u8eab\u4e0d\u5b58\u5728\u8be5\u5c5e\u6027&#xff0c;\u5904\u7406\u4f1a\u8fdb\u4e00\u6b65\u6d89\u53ca\u539f\u578b\u94fe&#xff1a;\u539f\u578b\u4e0a\u662f\u5426\u6709\u540c\u540d setter\u3001\u540c\u540d\u53ea\u8bfb\u5c5e\u6027\u6216\u5176\u4ed6\u63cf\u8ff0\u7b26&#xff0c;\u90fd\u4f1a\u5f71\u54cd\u6700\u7ec8\u80fd\u5426\u5728\u5f53\u524d\u5bf9\u8c61\u4e0a\u521b\u5efa\u65b0\u5c5e\u6027\u3002\u4e5f\u5c31\u662f\u8bf4&#xff0c;obj.key &#061; value \u5e76\u4e0d\u603b\u7b49\u4e8e\u201c\u65e0\u6761\u4ef6\u5728 obj \u4e0a\u5199\u5165\u4e00\u4e2a\u952e\u503c\u5bf9\u201d\u3002<\/p>\n<h3>5.3 Getter \u4e0e Setter<\/h3>\n<p>ES5 \u5141\u8bb8\u628a\u5c5e\u6027\u5b9a\u4e49\u6210\u8bbf\u95ee\u63cf\u8ff0\u7b26\u3002Getter \u662f\u8bfb\u53d6\u5c5e\u6027\u65f6\u81ea\u52a8\u8c03\u7528\u7684\u65e0\u53c2\u51fd\u6570&#xff0c;Setter \u662f\u5199\u5165\u5c5e\u6027\u65f6\u81ea\u52a8\u8c03\u7528\u3001\u63a5\u6536\u4e00\u4e2a\u65b0\u503c\u7684\u51fd\u6570\u3002\u4e0b\u9762\u540c\u65f6\u4f7f\u7528\u5bf9\u8c61\u5b57\u9762\u91cf\u548c Object.defineProperty() \u5b9a\u4e49 getter&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token comment\">\/\/ \u7ed9 a \u5b9a\u4e49\u4e00\u4e2a getter<\/span><br \/>\n    <span class=\"token keyword\">get<\/span> <span class=\"token function\">a<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token number\">2<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>Object<span class=\"token punctuation\">.<\/span><span class=\"token function\">defineProperty<\/span><span class=\"token punctuation\">(<\/span><br \/>\n    myObject<span class=\"token punctuation\">,<\/span> <span class=\"token comment\">\/\/ \u76ee\u6807\u5bf9\u8c61<\/span><br \/>\n    <span class=\"token string\">&#034;b&#034;<\/span><span class=\"token punctuation\">,<\/span>     <span class=\"token comment\">\/\/ \u5c5e\u6027\u540d<\/span><br \/>\n    <span class=\"token punctuation\">{<\/span>         <span class=\"token comment\">\/\/ \u63cf\u8ff0\u7b26<\/span><br \/>\n        <span class=\"token comment\">\/\/ \u7ed9 b \u5b9a\u4e49\u4e00\u4e2a getter<\/span><br \/>\n        <span class=\"token function-variable function\">get<\/span><span class=\"token operator\">:<\/span> <span class=\"token keyword\">function<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n            <span class=\"token keyword\">return<\/span> <span class=\"token keyword\">this<\/span><span class=\"token punctuation\">.<\/span>a <span class=\"token operator\">*<\/span> <span class=\"token number\">2<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">,<\/span><br \/>\n        <span class=\"token literal-property property\">enumerable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">true<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">.<\/span>a<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ 2<\/span><br \/>\nmyObject<span class=\"token punctuation\">.<\/span>b<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ 4<\/span><\/p>\n<p>\u8bfb\u53d6 a \u65f6&#xff0c;\u5176 getter \u8fd4\u56de 2&#xff1b;\u8bfb\u53d6 b \u65f6&#xff0c;b \u7684 getter \u518d\u8bbf\u95ee this.a&#xff0c;\u89e6\u53d1 a \u7684 getter\u5e76\u5f97\u5230 2&#xff0c;\u6700\u7ec8\u8fd4\u56de 4\u3002\u4e00\u65e6\u4e3a\u5c5e\u6027\u5b9a\u4e49 getter \u6216 setter&#xff0c;\u8fd9\u4e2a\u5c5e\u6027\u5c31\u6210\u4e3a\u8bbf\u95ee\u5668\u5c5e\u6027&#xff0c;\u63cf\u8ff0\u7b26\u4e2d\u7684 value \u4e0e writable \u4e0d\u518d\u9002\u7528&#xff0c;\u771f\u6b63\u63a7\u5236\u8bfb\u5199\u7684\u662f get \u4e0e set\u3002<\/p>\n<p>\u5982\u679c\u53ea\u5b9a\u4e49 getter&#xff0c;\u6ca1\u6709\u5b9a\u4e49 setter&#xff0c;\u90a3\u4e48\u8d4b\u503c\u64cd\u4f5c\u65e0\u6cd5\u4fdd\u5b58\u65b0\u503c&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token comment\">\/\/ \u7ed9 a \u5b9a\u4e49\u4e00\u4e2a getter<\/span><br \/>\n    <span class=\"token keyword\">get<\/span> <span class=\"token function\">a<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token number\">2<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">.<\/span>a <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">3<\/span><span class=\"token punctuation\">;<\/span><br \/>\nmyObject<span class=\"token punctuation\">.<\/span>a<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ 2<\/span><\/p>\n<p>\u975e\u4e25\u683c\u6a21\u5f0f\u4e0b&#xff0c;myObject.a &#061; 3 \u88ab\u5ffd\u7565&#xff1b;\u4e25\u683c\u6a21\u5f0f\u4e0b\u4f1a\u629b\u51fa TypeError\u3002\u65e0\u8bba\u5982\u4f55&#xff0c;\u4e0b\u4e00\u6b21\u8bfb\u53d6\u4ecd\u7136\u6267\u884c getter\u5e76\u8fd4\u56de\u56fa\u5b9a\u7684 2\u3002<\/p>\n<p>\u66f4\u5b8c\u6574\u7684\u8bbe\u8ba1\u901a\u5e38\u8ba9 getter \u548c setter \u6210\u5bf9\u51fa\u73b0&#xff0c;\u5e76\u4f7f\u7528\u53e6\u4e00\u4e2a\u666e\u901a\u5c5e\u6027\u4fdd\u5b58\u5185\u90e8\u72b6\u6001&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token comment\">\/\/ \u7ed9 a \u5b9a\u4e49\u4e00\u4e2a getter<\/span><br \/>\n    <span class=\"token keyword\">get<\/span> <span class=\"token function\">a<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token keyword\">this<\/span><span class=\"token punctuation\">.<\/span>_a<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">,<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u7ed9 a \u5b9a\u4e49\u4e00\u4e2a setter<\/span><br \/>\n    <span class=\"token keyword\">set<\/span> <span class=\"token function\">a<\/span><span class=\"token punctuation\">(<\/span><span class=\"token parameter\">val<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token keyword\">this<\/span><span class=\"token punctuation\">.<\/span>_a <span class=\"token operator\">&#061;<\/span> val <span class=\"token operator\">*<\/span> <span class=\"token number\">2<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">.<\/span>a <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">2<\/span><span class=\"token punctuation\">;<\/span><br \/>\nmyObject<span class=\"token punctuation\">.<\/span>a<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ 4<\/span><\/p>\n<p>\u6267\u884c myObject.a &#061; 2 \u65f6&#xff0c;[[Put]] \u53d1\u73b0 a \u662f\u8bbf\u95ee\u5668\u5c5e\u6027&#xff0c;\u4e8e\u662f\u8c03\u7528 setter\u3002Setter \u5e76\u4e0d\u76f4\u63a5\u4fdd\u5b58 2&#xff0c;\u800c\u662f\u628a 2 * 2 \u5199\u5165 _a\u3002\u968f\u540e\u8bfb\u53d6 myObject.a&#xff0c;getter \u8fd4\u56de _a&#xff0c;\u6240\u4ee5\u7ed3\u679c\u662f 4\u3002\u8fd9\u91cc\u7684\u4e0b\u5212\u7ebf\u53ea\u662f\u4e00\u79cd\u547d\u540d\u7ea6\u5b9a&#xff0c;\u5e76\u4e0d\u4f1a\u8ba9 _a \u81ea\u52a8\u53d8\u6210\u771f\u6b63\u7684\u79c1\u6709\u5c5e\u6027\u3002<\/p>\n<h2>6. \u5c5e\u6027\u5b58\u5728\u6027\u4e0e\u53ef\u679a\u4e3e\u6027<\/h2>\n<h3>6.1 in \u4e0e\u81ea\u6709\u5c5e\u6027\u68c0\u67e5<\/h3>\n<p>\u5c5e\u6027\u503c\u53ef\u80fd\u6070\u597d\u662f undefined&#xff0c;\u56e0\u6b64\u5b58\u5728\u6027\u5fc5\u987b\u5355\u72ec\u68c0\u67e5\u3002in \u548c hasOwnProperty() \u7684\u5173\u952e\u5dee\u522b\u5728\u4e8e\u662f\u5426\u68c0\u67e5\u539f\u578b\u94fe&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">a<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">2<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;a&#034;<\/span> <span class=\"token keyword\">in<\/span> myObject<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ true<\/span><br \/>\n<span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;b&#034;<\/span> <span class=\"token keyword\">in<\/span> myObject<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ false<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">.<\/span><span class=\"token function\">hasOwnProperty<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;a&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ true<\/span><br \/>\nmyObject<span class=\"token punctuation\">.<\/span><span class=\"token function\">hasOwnProperty<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;b&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ false<\/span><\/p>\n<p>&#034;a&#034; in myObject \u4f1a\u5148\u68c0\u67e5\u5bf9\u8c61\u81ea\u8eab&#xff0c;\u518d\u6cbf [[Prototype]] \u94fe\u5411\u4e0a\u67e5\u627e&#xff1b;myObject.hasOwnProperty(&#034;a&#034;) \u53ea\u68c0\u67e5 myObject \u672c\u8eab\u3002\u4e8c\u8005\u5224\u65ad\u7684\u90fd\u662f\u5c5e\u6027\u540d\u662f\u5426\u5b58\u5728&#xff0c;\u5e76\u4e0d\u641c\u7d22\u67d0\u4e2a\u5c5e\u6027\u503c\u3002<\/p>\n<p>\u5f53\u5bf9\u8c61\u901a\u8fc7 Object.create(null) \u521b\u5efa\u65f6&#xff0c;\u5b83\u6ca1\u6709\u7ee7\u627f Object.prototype&#xff0c;\u56e0\u800c\u6ca1\u6709 hasOwnProperty()&#xff1b;\u666e\u901a\u5bf9\u8c61\u4e5f\u53ef\u80fd\u5b9a\u4e49\u540c\u540d\u5c5e\u6027&#xff0c;\u906e\u853d\u7ee7\u627f\u6765\u7684\u65b9\u6cd5\u3002\u4f20\u7edf\u7684\u7a33\u59a5\u5199\u6cd5\u662f&#xff1a;<\/p>\n<p><span class=\"token class-name\">Object<\/span><span class=\"token punctuation\">.<\/span>prototype<span class=\"token punctuation\">.<\/span><span class=\"token function\">hasOwnProperty<\/span><span class=\"token punctuation\">.<\/span><span class=\"token function\">call<\/span><span class=\"token punctuation\">(<\/span>myObject<span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;a&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>\u5728\u73b0\u4ee3\u8fd0\u884c\u73af\u5883\u4e2d&#xff0c;\u4e5f\u53ef\u4ee5\u76f4\u63a5\u4f7f\u7528\u4e0d\u4f1a\u53d7\u540c\u540d\u5c5e\u6027\u5e72\u6270\u7684 Object.hasOwn(myObject, &#034;a&#034;)\u3002<\/p>\n<p>\u6570\u7ec4\u793a\u4f8b\u5c24\u5176\u80fd\u8bf4\u660e in \u68c0\u67e5\u7684\u662f\u7d22\u5f15\u952e\u800c\u4e0d\u662f\u5143\u7d20\u503c&#xff1a;<\/p>\n<p><span class=\"token number\">4<\/span> <span class=\"token keyword\">in<\/span> <span class=\"token punctuation\">[<\/span><span class=\"token number\">2<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">4<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">6<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ false<\/span><\/p>\n<p>\u6570\u7ec4 [2, 4, 6] \u62e5\u6709\u7684\u7d22\u5f15\u662f 0\u30011\u30012&#xff0c;\u867d\u7136\u5176\u4e2d\u5305\u542b\u503c 4&#xff0c;\u5374\u6ca1\u6709\u7d22\u5f15 4&#xff0c;\u6240\u4ee5\u7ed3\u679c\u662f false\u3002<\/p>\n<h3>6.2 \u679a\u4e3e\u3001\u5c5e\u6027\u540d\u5217\u8868\u4e0e\u68c0\u67e5\u8fb9\u754c<\/h3>\n<p>\u5b58\u5728\u7684\u5c5e\u6027\u4e0d\u4e00\u5b9a\u53ef\u679a\u4e3e\u3002\u4e0b\u9762\u521b\u5efa\u4e00\u4e2a\u53ef\u679a\u4e3e\u7684 a \u548c\u4e00\u4e2a\u4e0d\u53ef\u679a\u4e3e\u7684 b&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>Object<span class=\"token punctuation\">.<\/span><span class=\"token function\">defineProperty<\/span><span class=\"token punctuation\">(<\/span>myObject<span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;a&#034;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">enumerable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">true<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">value<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">2<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>Object<span class=\"token punctuation\">.<\/span><span class=\"token function\">defineProperty<\/span><span class=\"token punctuation\">(<\/span>myObject<span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;b&#034;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">enumerable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">false<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">value<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">3<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">.<\/span>b<span class=\"token punctuation\">;<\/span>                    <span class=\"token comment\">\/\/ 3<\/span><br \/>\n<span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;b&#034;<\/span> <span class=\"token keyword\">in<\/span> myObject<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span>            <span class=\"token comment\">\/\/ true<\/span><br \/>\nmyObject<span class=\"token punctuation\">.<\/span><span class=\"token function\">hasOwnProperty<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;b&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ true<\/span><\/p>\n<p><span class=\"token keyword\">for<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">var<\/span> k <span class=\"token keyword\">in<\/span> myObject<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    console<span class=\"token punctuation\">.<\/span><span class=\"token function\">log<\/span><span class=\"token punctuation\">(<\/span>k<span class=\"token punctuation\">,<\/span> myObject<span class=\"token punctuation\">[<\/span>k<span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><br \/>\n<span class=\"token comment\">\/\/ &#034;a&#034; 2<\/span><\/p>\n<p>\u5c5e\u6027 b \u53ef\u4ee5\u8bfb\u53d6&#xff0c;\u4e5f\u786e\u5b9e\u662f\u5bf9\u8c61\u7684\u81ea\u6709\u5c5e\u6027&#xff0c;\u53ea\u662f for&#8230;in \u4e0d\u4f1a\u679a\u4e3e\u5b83\u3002for&#8230;in \u8fd8\u4f1a\u6cbf\u539f\u578b\u94fe\u679a\u4e3e\u53ef\u679a\u4e3e\u5c5e\u6027&#xff0c;\u56e0\u6b64\u5904\u7406\u666e\u901a\u5bf9\u8c61\u65f6\u901a\u5e38\u9700\u8981\u914d\u5408\u81ea\u6709\u5c5e\u6027\u68c0\u67e5\u3002\u5bf9\u4e8e\u6570\u7ec4&#xff0c;for&#8230;in \u8fd8\u53ef\u80fd\u5217\u51fa\u540e\u6765\u6dfb\u52a0\u7684\u666e\u901a\u5c5e\u6027&#xff0c;\u4e0d\u9002\u5408\u66ff\u4ee3\u6309\u7d22\u5f15\u904d\u5386\u3002<\/p>\n<p>\u8fd8\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b API \u7cbe\u786e\u89c2\u5bdf\u81ea\u6709\u5c5e\u6027&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>Object<span class=\"token punctuation\">.<\/span><span class=\"token function\">defineProperty<\/span><span class=\"token punctuation\">(<\/span>myObject<span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;a&#034;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">enumerable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">true<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">value<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">2<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>Object<span class=\"token punctuation\">.<\/span><span class=\"token function\">defineProperty<\/span><span class=\"token punctuation\">(<\/span>myObject<span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;b&#034;<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">enumerable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">false<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">value<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">3<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>myObject<span class=\"token punctuation\">.<\/span><span class=\"token function\">propertyIsEnumerable<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;a&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ true<\/span><br \/>\nmyObject<span class=\"token punctuation\">.<\/span><span class=\"token function\">propertyIsEnumerable<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;b&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ false<\/span><\/p>\n<p>Object<span class=\"token punctuation\">.<\/span><span class=\"token function\">keys<\/span><span class=\"token punctuation\">(<\/span>myObject<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span>                <span class=\"token comment\">\/\/ [&#034;a&#034;]<\/span><br \/>\nObject<span class=\"token punctuation\">.<\/span><span class=\"token function\">getOwnPropertyNames<\/span><span class=\"token punctuation\">(<\/span>myObject<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ [&#034;a&#034;, &#034;b&#034;]<\/span><\/p>\n<table>\n<tr>\u68c0\u67e5\u65b9\u5f0f\u81ea\u6709\u5c5e\u6027\u539f\u578b\u94fe\u5c5e\u6027\u4e0d\u53ef\u679a\u4e3e\u5c5e\u6027\u8fd4\u56de\u5185\u5bb9<\/tr>\n<tbody>\n<tr>\n<td>key in obj<\/td>\n<td>\u662f<\/td>\n<td>\u662f<\/td>\n<td>\u662f<\/td>\n<td>\u5e03\u5c14\u503c<\/td>\n<\/tr>\n<tr>\n<td>obj.hasOwnProperty(key)<\/td>\n<td>\u662f<\/td>\n<td>\u5426<\/td>\n<td>\u662f<\/td>\n<td>\u5e03\u5c14\u503c<\/td>\n<\/tr>\n<tr>\n<td>obj.propertyIsEnumerable(key)<\/td>\n<td>\u662f<\/td>\n<td>\u5426<\/td>\n<td>\u5426<\/td>\n<td>\u5e03\u5c14\u503c<\/td>\n<\/tr>\n<tr>\n<td>Object.keys(obj)<\/td>\n<td>\u662f<\/td>\n<td>\u5426<\/td>\n<td>\u5426<\/td>\n<td>\u53ef\u679a\u4e3e\u5b57\u7b26\u4e32\u952e\u6570\u7ec4<\/td>\n<\/tr>\n<tr>\n<td>Object.getOwnPropertyNames(obj)<\/td>\n<td>\u662f<\/td>\n<td>\u5426<\/td>\n<td>\u662f<\/td>\n<td>\u5168\u90e8\u81ea\u6709\u5b57\u7b26\u4e32\u952e\u6570\u7ec4<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Symbol \u952e\u4e0d\u4f1a\u51fa\u73b0\u5728 Object.keys() \u6216 Object.getOwnPropertyNames() \u4e2d&#xff1b;\u786e\u6709\u9700\u8981\u65f6&#xff0c;\u53ef\u4ee5\u4f7f\u7528 Object.getOwnPropertySymbols() \u83b7\u53d6\u5bf9\u8c61\u81ea\u8eab\u7684 Symbol \u952e\u3002\u6ca1\u6709\u4e00\u4e2a\u5355\u72ec\u7684\u4f20\u7edf API \u4f1a\u4e00\u6b21\u8fd4\u56de\u5bf9\u8c61\u81ea\u8eab\u548c\u6574\u6761\u539f\u578b\u94fe\u4e0a\u7684\u5168\u90e8\u5c5e\u6027&#xff1b;\u9700\u8981\u8de8\u539f\u578b\u94fe\u6536\u96c6\u65f6&#xff0c;\u5e94\u660e\u786e\u9010\u5c42\u68c0\u67e5&#xff0c;\u907f\u514d\u628a\u7ee7\u627f\u5c5e\u6027\u548c\u81ea\u6709\u5c5e\u6027\u6df7\u4e3a\u4e00\u8c08\u3002<\/p>\n<h2>7. \u904d\u5386\u4e0e\u8fed\u4ee3\u534f\u8bae<\/h2>\n<h3>7.1 \u679a\u4e3e\u5c5e\u6027\u4e0e\u8fed\u4ee3\u503c<\/h3>\n<p>\u904d\u5386\u6570\u7ec4\u6700\u76f4\u63a5\u7684\u65b9\u5f0f\u662f\u6309\u4e0b\u6807\u8bfb\u53d6&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myArray <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">[<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">2<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">3<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p><span class=\"token keyword\">for<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">var<\/span> i <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span> i <span class=\"token operator\">&lt;<\/span> myArray<span class=\"token punctuation\">.<\/span>length<span class=\"token punctuation\">;<\/span> i<span class=\"token operator\">&#043;&#043;<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    console<span class=\"token punctuation\">.<\/span><span class=\"token function\">log<\/span><span class=\"token punctuation\">(<\/span>myArray<span class=\"token punctuation\">[<\/span>i<span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><br \/>\n<span class=\"token comment\">\/\/ 1 2 3<\/span><\/p>\n<p>\u8fd9\u91cc\u904d\u5386\u7684\u662f\u4ece 0 \u5230 length &#8211; 1 \u7684\u7d22\u5f15\u8303\u56f4\u3002ES5 \u53c8\u63d0\u4f9b\u4e86 forEach()\u3001every() \u548c some() \u7b49\u6570\u7ec4\u8f85\u52a9\u65b9\u6cd5&#xff0c;\u5b83\u4eec\u90fd\u628a\u56de\u8c03\u5e94\u7528\u5230\u6570\u7ec4\u5143\u7d20\u4e0a&#xff0c;\u4f46\u5bf9\u56de\u8c03\u8fd4\u56de\u503c\u7684\u5904\u7406\u4e0d\u540c&#xff1a;<\/p>\n<table>\n<tr>\u65b9\u6cd5\u56de\u8c03\u8fd4\u56de\u503c\u7684\u4f5c\u7528\u63d0\u524d\u7ed3\u675f\u6761\u4ef6<\/tr>\n<tbody>\n<tr>\n<td>forEach()<\/td>\n<td>\u8fd4\u56de\u503c\u88ab\u5ffd\u7565<\/td>\n<td>\u4e0d\u80fd\u9760\u666e\u901a return \u63d0\u524d\u7ed3\u675f\u6574\u4f53\u904d\u5386<\/td>\n<\/tr>\n<tr>\n<td>every()<\/td>\n<td>\u5224\u65ad\u6240\u6709\u5143\u7d20\u662f\u5426\u6ee1\u8db3\u6761\u4ef6<\/td>\n<td>\u9996\u6b21\u8fd4\u56de\u5047\u503c\u65f6\u7ed3\u675f<\/td>\n<\/tr>\n<tr>\n<td>some()<\/td>\n<td>\u5224\u65ad\u662f\u5426\u81f3\u5c11\u4e00\u4e2a\u5143\u7d20\u6ee1\u8db3\u6761\u4ef6<\/td>\n<td>\u9996\u6b21\u8fd4\u56de\u771f\u503c\u65f6\u7ed3\u675f<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>for&#8230;in \u679a\u4e3e\u7684\u662f\u5bf9\u8c61\u5c5e\u6027\u540d&#xff0c;for&#8230;of \u8fed\u4ee3\u7684\u662f\u53ef\u8fed\u4ee3\u5bf9\u8c61\u4ea7\u751f\u7684\u503c\u3002\u4e8c\u8005\u89e3\u51b3\u7684\u95ee\u9898\u4e0d\u540c&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myArray <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">[<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">2<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">3<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p><span class=\"token keyword\">for<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">var<\/span> v <span class=\"token keyword\">of<\/span> myArray<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    console<span class=\"token punctuation\">.<\/span><span class=\"token function\">log<\/span><span class=\"token punctuation\">(<\/span>v<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><br \/>\n<span class=\"token comment\">\/\/ 1<\/span><br \/>\n<span class=\"token comment\">\/\/ 2<\/span><br \/>\n<span class=\"token comment\">\/\/ 3<\/span><\/p>\n<p>\u5373\u4f7f\u67d0\u4e9b\u73af\u5883\u4e3a\u5c5e\u6027\u952e\u5b9a\u4e49\u4e86\u7a33\u5b9a\u7684\u679a\u4e3e\u6b21\u5e8f&#xff0c;\u4e5f\u4e0d\u5e94\u8be5\u628a for&#8230;in \u5f53\u4f5c\u6570\u7ec4\u6392\u5e8f\u6216\u503c\u904d\u5386\u5de5\u5177\u3002\u6570\u7ec4\u503c\u904d\u5386\u4f18\u5148\u9009\u62e9 for&#8230;of\u3001\u6570\u7ec4\u8fed\u4ee3\u65b9\u6cd5\u6216\u4f20\u7edf\u7d22\u5f15\u5faa\u73af\u3002<\/p>\n<h3>7.2 \u8fed\u4ee3\u5668\u534f\u8bae\u4e0e\u81ea\u5b9a\u4e49\u8fed\u4ee3\u5668<\/h3>\n<p>for&#8230;of \u5e76\u4e0d\u662f\u786c\u7f16\u7801\u53ea\u8ba4\u8bc6\u6570\u7ec4\u3002\u5b83\u4f1a\u5148\u5411\u76ee\u6807\u8bf7\u6c42 Symbol.iterator \u65b9\u6cd5&#xff0c;\u901a\u8fc7\u8be5\u65b9\u6cd5\u53d6\u5f97\u4e00\u4e2a\u8fed\u4ee3\u5668\u5bf9\u8c61&#xff1b;\u968f\u540e\u53cd\u590d\u8c03\u7528\u8fed\u4ee3\u5668\u7684 next()&#xff0c;\u8bfb\u53d6\u8fd4\u56de\u5bf9\u8c61\u4e2d\u7684 value \u548c done\u3002\u5f53 done \u4e3a true \u65f6&#xff0c;\u5faa\u73af\u7ed3\u675f\u3002<\/p>\n<p>\u6570\u7ec4\u5df2\u7ecf\u5185\u7f6e\u4e86 Symbol.iterator&#xff0c;\u56e0\u6b64\u53ef\u4ee5\u624b\u52a8\u89c2\u5bdf\u8fed\u4ee3\u8fc7\u7a0b&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myArray <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">[<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">2<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">3<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token keyword\">var<\/span> it <span class=\"token operator\">&#061;<\/span> myArray<span class=\"token punctuation\">[<\/span>Symbol<span class=\"token punctuation\">.<\/span>iterator<span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>it<span class=\"token punctuation\">.<\/span><span class=\"token function\">next<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ { value: 1, done: false }<\/span><br \/>\nit<span class=\"token punctuation\">.<\/span><span class=\"token function\">next<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ { value: 2, done: false }<\/span><br \/>\nit<span class=\"token punctuation\">.<\/span><span class=\"token function\">next<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ { value: 3, done: false }<\/span><br \/>\nit<span class=\"token punctuation\">.<\/span><span class=\"token function\">next<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ { value: undefined, done: true }<\/span><\/p>\n<p>\u8c03\u7528 Symbol.iterator \u5f97\u5230\u7684\u662f\u8fed\u4ee3\u5668&#xff0c;\u8c03\u7528 next() \u624d\u9010\u6b65\u6d88\u8d39\u6570\u636e\u3002\u666e\u901a\u5bf9\u8c61\u9ed8\u8ba4\u6ca1\u6709\u5185\u7f6e\u8fed\u4ee3\u5668&#xff0c;\u56e0\u4e3a\u5bf9\u8c61\u5c5e\u6027\u5e76\u4e0d\u5929\u7136\u4ee3\u8868\u67d0\u4e00\u79cd\u552f\u4e00\u7684\u503c\u5e8f\u5217\u3002\u4e0d\u8fc7&#xff0c;\u53ef\u4ee5\u4e3b\u52a8\u7ed9\u5bf9\u8c61\u5b9a\u4e49\u8fed\u4ee3\u89c4\u5219&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> myObject <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">a<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">2<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">b<\/span><span class=\"token operator\">:<\/span> <span class=\"token number\">3<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>Object<span class=\"token punctuation\">.<\/span><span class=\"token function\">defineProperty<\/span><span class=\"token punctuation\">(<\/span>myObject<span class=\"token punctuation\">,<\/span> Symbol<span class=\"token punctuation\">.<\/span>iterator<span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token literal-property property\">enumerable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">false<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">writable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">false<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token literal-property property\">configurable<\/span><span class=\"token operator\">:<\/span> <span class=\"token boolean\">true<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token function-variable function\">value<\/span><span class=\"token operator\">:<\/span> <span class=\"token keyword\">function<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token keyword\">var<\/span> o <span class=\"token operator\">&#061;<\/span> <span class=\"token keyword\">this<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">var<\/span> idx <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">var<\/span> ks <span class=\"token operator\">&#061;<\/span> Object<span class=\"token punctuation\">.<\/span><span class=\"token function\">keys<\/span><span class=\"token punctuation\">(<\/span>o<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>        <span class=\"token keyword\">return<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n            <span class=\"token function-variable function\">next<\/span><span class=\"token operator\">:<\/span> <span class=\"token keyword\">function<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n                <span class=\"token keyword\">return<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n                    <span class=\"token literal-property property\">value<\/span><span class=\"token operator\">:<\/span> o<span class=\"token punctuation\">[<\/span>ks<span class=\"token punctuation\">[<\/span>idx<span class=\"token operator\">&#043;&#043;<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">,<\/span><br \/>\n                    <span class=\"token literal-property property\">done<\/span><span class=\"token operator\">:<\/span> idx <span class=\"token operator\">&gt;<\/span> ks<span class=\"token punctuation\">.<\/span>length<br \/>\n                <span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><br \/>\n            <span class=\"token punctuation\">}<\/span><br \/>\n        <span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>\u8fd9\u91cc\u5148\u7528 Object.keys(o) \u56fa\u5b9a\u672c\u6b21\u8981\u8fed\u4ee3\u7684\u81ea\u6709\u53ef\u679a\u4e3e\u5b57\u7b26\u4e32\u952e&#xff0c;\u518d\u7528 idx \u8bb0\u5f55\u8fdb\u5ea6\u3002\u6bcf\u6b21 next() \u8bfb\u53d6\u5f53\u524d\u952e\u5bf9\u5e94\u7684\u503c\u5e76\u9012\u589e\u4e0b\u6807&#xff1b;\u5f53\u4e0b\u6807\u8d8a\u8fc7\u952e\u6570\u7ec4\u957f\u5ea6\u65f6&#xff0c;done \u53d8\u6210 true\u3002\u624b\u52a8\u8c03\u7528\u53ef\u4ee5\u770b\u5230\u72b6\u6001\u53d8\u5316&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> it <span class=\"token operator\">&#061;<\/span> myObject<span class=\"token punctuation\">[<\/span>Symbol<span class=\"token punctuation\">.<\/span>iterator<span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>it<span class=\"token punctuation\">.<\/span><span class=\"token function\">next<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ { value: 2, done: false }<\/span><br \/>\nit<span class=\"token punctuation\">.<\/span><span class=\"token function\">next<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ { value: 3, done: false }<\/span><br \/>\nit<span class=\"token punctuation\">.<\/span><span class=\"token function\">next<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ { value: undefined, done: true }<\/span><\/p>\n<p>\u5b9a\u4e49\u8fed\u4ee3\u5668\u4ee5\u540e&#xff0c;\u666e\u901a\u5bf9\u8c61\u4e5f\u80fd\u76f4\u63a5\u53c2\u4e0e for&#8230;of&#xff1a;<\/p>\n<p><span class=\"token keyword\">for<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">var<\/span> v <span class=\"token keyword\">of<\/span> myObject<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    console<span class=\"token punctuation\">.<\/span><span class=\"token function\">log<\/span><span class=\"token punctuation\">(<\/span>v<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><br \/>\n<span class=\"token comment\">\/\/ 2<\/span><br \/>\n<span class=\"token comment\">\/\/ 3<\/span><\/p>\n<p>ES6 \u7684\u53ef\u8ba1\u7b97\u5c5e\u6027\u540d\u4e5f\u80fd\u76f4\u63a5\u5b9a\u4e49 Symbol.iterator\u3002\u4e0b\u9762\u6784\u9020\u4e00\u4e2a\u4e0d\u4f1a\u4e3b\u52a8\u7ed3\u675f\u7684\u968f\u673a\u6570\u751f\u6210\u5668&#xff1a;<\/p>\n<p><span class=\"token keyword\">var<\/span> randoms <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token punctuation\">[<\/span>Symbol<span class=\"token punctuation\">.<\/span>iterator<span class=\"token punctuation\">]<\/span><span class=\"token operator\">:<\/span> <span class=\"token keyword\">function<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n            <span class=\"token function-variable function\">next<\/span><span class=\"token operator\">:<\/span> <span class=\"token keyword\">function<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n                <span class=\"token keyword\">return<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n                    <span class=\"token literal-property property\">value<\/span><span class=\"token operator\">:<\/span> Math<span class=\"token punctuation\">.<\/span><span class=\"token function\">random<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><br \/>\n                <span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><br \/>\n            <span class=\"token punctuation\">}<\/span><br \/>\n        <span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p><span class=\"token keyword\">var<\/span> randoms_pool <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">[<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p><span class=\"token keyword\">for<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">var<\/span> n <span class=\"token keyword\">of<\/span> randoms<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    randoms_pool<span class=\"token punctuation\">.<\/span><span class=\"token function\">push<\/span><span class=\"token punctuation\">(<\/span>n<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u9632\u6b62\u65e0\u9650\u8fd0\u884c<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>randoms_pool<span class=\"token punctuation\">.<\/span>length <span class=\"token operator\">&#061;&#061;&#061;<\/span> <span class=\"token number\">100<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token keyword\">break<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n<p>\u8fd9\u4e2a next() 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