{"id":1389,"date":"2024-06-02T22:33:22","date_gmt":"2024-06-02T22:33:22","guid":{"rendered":""},"modified":"2024-06-05T06:12:19","modified_gmt":"2024-06-04T22:12:19","slug":"javascript%e6%b7%b1%e5%85%a5%e4%b9%8b%e5%8f%98%e9%87%8f%e5%af%b9%e8%b1%a1","status":"publish","type":"post","link":"https:\/\/www.lccc.top\/?p=1389","title":{"rendered":"JavaScript\u6df1\u5165\u4e4b\u53d8\u91cf\u5bf9\u8c61"},"content":{"rendered":"<td class=\"d-block comment-body markdown-body  js-comment-body\">\n<h2 dir=\"auto\">\u524d\u8a00<\/h2>\n<p dir=\"auto\">\u5728\u4e0a\u7bc7<a href=\"https:\/\/github.com\/mqyqingfeng\/Blog\/issues\/4\" data-hovercard-type=\"issue\" data-hovercard-url=\"\/mqyqingfeng\/Blog\/issues\/4\/hovercard\">\u300aJavaScript\u6df1\u5165\u4e4b\u6267\u884c\u4e0a\u4e0b\u6587\u6808\u300b<\/a>\u4e2d\u8bb2\u5230\uff0c\u5f53 JavaScript \u4ee3\u7801\u6267\u884c\u4e00\u6bb5\u53ef\u6267\u884c\u4ee3\u7801(executable code)\u65f6\uff0c\u4f1a\u521b\u5efa\u5bf9\u5e94\u7684\u6267\u884c\u4e0a\u4e0b\u6587(execution context)\u3002<\/p>\n<p dir=\"auto\">\u5bf9\u4e8e\u6bcf\u4e2a\u6267\u884c\u4e0a\u4e0b\u6587\uff0c\u90fd\u6709\u4e09\u4e2a\u91cd\u8981\u5c5e\u6027\uff1a<\/p>\n<ul dir=\"auto\">\n<li>\u53d8\u91cf\u5bf9\u8c61(Variable object\uff0cVO)<\/li>\n<li>\u4f5c\u7528\u57df\u94fe(Scope chain)<\/li>\n<li>this<\/li>\n<\/ul>\n<p dir=\"auto\">\u4eca\u5929\u91cd\u70b9\u8bb2\u8bb2\u521b\u5efa\u53d8\u91cf\u5bf9\u8c61\u7684\u8fc7\u7a0b\u3002<\/p>\n<h2 dir=\"auto\">\u53d8\u91cf\u5bf9\u8c61<\/h2>\n<p dir=\"auto\">\u53d8\u91cf\u5bf9\u8c61\u662f\u4e0e\u6267\u884c\u4e0a\u4e0b\u6587\u76f8\u5173\u7684\u6570\u636e\u4f5c\u7528\u57df\uff0c\u5b58\u50a8\u4e86\u5728\u4e0a\u4e0b\u6587\u4e2d\u5b9a\u4e49\u7684\u53d8\u91cf\u548c\u51fd\u6570\u58f0\u660e\u3002<\/p>\n<p dir=\"auto\">\u56e0\u4e3a\u4e0d\u540c\u6267\u884c\u4e0a\u4e0b\u6587\u4e0b\u7684\u53d8\u91cf\u5bf9\u8c61\u7a0d\u6709\u4e0d\u540c\uff0c\u6240\u4ee5\u6211\u4eec\u6765\u804a\u804a\u5168\u5c40\u4e0a\u4e0b\u6587\u4e0b\u7684\u53d8\u91cf\u5bf9\u8c61\u548c\u51fd\u6570\u4e0a\u4e0b\u6587\u4e0b\u7684\u53d8\u91cf\u5bf9\u8c61\u3002<\/p>\n<h2 dir=\"auto\">\u5168\u5c40\u4e0a\u4e0b\u6587<\/h2>\n<p dir=\"auto\">\u6211\u4eec\u5148\u4e86\u89e3\u4e00\u4e2a\u6982\u5ff5\uff0c\u53eb\u5168\u5c40\u5bf9\u8c61\u3002\u5728 <a href=\"http:\/\/www.w3school.com.cn\/jsref\/jsref_obj_global.asp\" rel=\"nofollow\">W3School<\/a> \u4e2d\u4e5f\u6709\u4ecb\u7ecd\uff1a<\/p>\n<blockquote>\n<p dir=\"auto\">\u5168\u5c40\u5bf9\u8c61\u662f\u9884\u5b9a\u4e49\u7684\u5bf9\u8c61\uff0c\u4f5c\u4e3a JavaScript \u7684\u5168\u5c40\u51fd\u6570\u548c\u5168\u5c40\u5c5e\u6027\u7684\u5360\u4f4d\u7b26\u3002\u901a\u8fc7\u4f7f\u7528\u5168\u5c40\u5bf9\u8c61\uff0c\u53ef\u4ee5\u8bbf\u95ee\u6240\u6709\u5176\u4ed6\u6240\u6709\u9884\u5b9a\u4e49\u7684\u5bf9\u8c61\u3001\u51fd\u6570\u548c\u5c5e\u6027\u3002<\/p>\n<\/blockquote>\n<blockquote>\n<p dir=\"auto\">\u5728\u9876\u5c42 JavaScript \u4ee3\u7801\u4e2d\uff0c\u53ef\u4ee5\u7528\u5173\u952e\u5b57 this \u5f15\u7528\u5168\u5c40\u5bf9\u8c61\u3002\u56e0\u4e3a\u5168\u5c40\u5bf9\u8c61\u662f\u4f5c\u7528\u57df\u94fe\u7684\u5934\uff0c\u8fd9\u610f\u5473\u7740\u6240\u6709\u975e\u9650\u5b9a\u6027\u7684\u53d8\u91cf\u548c\u51fd\u6570\u540d\u90fd\u4f1a\u4f5c\u4e3a\u8be5\u5bf9\u8c61\u7684\u5c5e\u6027\u6765\u67e5\u8be2\u3002<\/p>\n<\/blockquote>\n<blockquote>\n<p dir=\"auto\">\u4f8b\u5982\uff0c\u5f53JavaScript \u4ee3\u7801\u5f15\u7528 parseInt() \u51fd\u6570\u65f6\uff0c\u5b83\u5f15\u7528\u7684\u662f\u5168\u5c40\u5bf9\u8c61\u7684 parseInt \u5c5e\u6027\u3002\u5168\u5c40\u5bf9\u8c61\u662f\u4f5c\u7528\u57df\u94fe\u7684\u5934\uff0c\u8fd8\u610f\u5473\u7740\u5728\u9876\u5c42 JavaScript \u4ee3\u7801\u4e2d\u58f0\u660e\u7684\u6240\u6709\u53d8\u91cf\u90fd\u5c06\u6210\u4e3a\u5168\u5c40\u5bf9\u8c61\u7684\u5c5e\u6027\u3002<\/p>\n<\/blockquote>\n<p dir=\"auto\">\u5982\u679c\u770b\u7684\u4e0d\u662f\u5f88\u61c2\u7684\u8bdd\uff0c\u5bb9\u6211\u518d\u6765\u4ecb\u7ecd\u4e0b\u5168\u5c40\u5bf9\u8c61:<\/p>\n<p dir=\"auto\">1.\u53ef\u4ee5\u901a\u8fc7 this \u5f15\u7528\uff0c\u5728\u5ba2\u6237\u7aef JavaScript \u4e2d\uff0c\u5168\u5c40\u5bf9\u8c61\u5c31\u662f Window \u5bf9\u8c61\u3002<\/p>\n<div class=\"highlight highlight-source-js notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content=\"console.log(this);\">\n<pre class=\"notranslate\"><span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-smi\">this<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span><\/pre>\n<\/div>\n<p dir=\"auto\">2.\u5168\u5c40\u5bf9\u8c61\u662f\u7531 Object \u6784\u9020\u51fd\u6570\u5b9e\u4f8b\u5316\u7684\u4e00\u4e2a\u5bf9\u8c61\u3002<\/p>\n<div class=\"highlight highlight-source-js notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content=\"console.log(this instanceof Object);\">\n<pre class=\"notranslate\"><span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-smi\">this<\/span> <span class=\"pl-k\">instanceof<\/span> <span class=\"pl-v\">Object<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span><\/pre>\n<\/div>\n<p dir=\"auto\">3.\u9884\u5b9a\u4e49\u4e86\u4e00\u5806\uff0c\u55ef\uff0c\u4e00\u5927\u5806\u51fd\u6570\u548c\u5c5e\u6027\u3002<\/p>\n<div class=\"highlight highlight-source-js notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content=\"\/\/ \u90fd\u80fd\u751f\u6548\nconsole.log(Math.random());\nconsole.log(this.Math.random());\"><\/p>\n<pre class=\"notranslate\"><span class=\"pl-c\">\/\/ \u90fd\u80fd\u751f\u6548<\/span>\n<span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-v\">Math<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">random<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-smi\">this<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-c1\">Math<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">random<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span><\/pre>\n<\/div>\n<p dir=\"auto\">4.\u4f5c\u4e3a\u5168\u5c40\u53d8\u91cf\u7684\u5bbf\u4e3b\u3002<\/p>\n<div class=\"highlight highlight-source-js notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content=\"var a = 1;\nconsole.log(this.a);\"><\/p>\n<pre class=\"notranslate\"><span class=\"pl-k\">var<\/span> <span class=\"pl-s1\">a<\/span> <span class=\"pl-c1\">=<\/span> <span class=\"pl-c1\">1<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-smi\">this<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-c1\">a<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span><\/pre>\n<\/div>\n<p dir=\"auto\">5.\u5ba2\u6237\u7aef JavaScript \u4e2d\uff0c\u5168\u5c40\u5bf9\u8c61\u6709 window \u5c5e\u6027\u6307\u5411\u81ea\u8eab\u3002<\/p>\n<div class=\"highlight highlight-source-js notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content=\"var a = 1;\nconsole.log(window.a);\n\nthis.window.b = 2;\nconsole.log(this.b);\"><\/p>\n<pre class=\"notranslate\"><span class=\"pl-k\">var<\/span> <span class=\"pl-s1\">a<\/span> <span class=\"pl-c1\">=<\/span> <span class=\"pl-c1\">1<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-smi\">window<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-c1\">a<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n\n<span class=\"pl-smi\">this<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-c1\">window<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-c1\">b<\/span> <span class=\"pl-c1\">=<\/span> <span class=\"pl-c1\">2<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-smi\">this<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-c1\">b<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span><\/pre>\n<\/div>\n<p dir=\"auto\">\u82b1\u4e86\u4e00\u4e2a\u5927\u7bc7\u5e45\u4ecb\u7ecd\u5168\u5c40\u5bf9\u8c61\uff0c\u5176\u5b9e\u5c31\u60f3\u8bf4\uff1a<\/p>\n<p dir=\"auto\">\u5168\u5c40\u4e0a\u4e0b\u6587\u4e2d\u7684\u53d8\u91cf\u5bf9\u8c61\u5c31\u662f\u5168\u5c40\u5bf9\u8c61\u5450\uff01<\/p>\n<h2 dir=\"auto\">\u51fd\u6570\u4e0a\u4e0b\u6587<\/h2>\n<p dir=\"auto\">\u5728\u51fd\u6570\u4e0a\u4e0b\u6587\u4e2d\uff0c\u6211\u4eec\u7528\u6d3b\u52a8\u5bf9\u8c61(activation object, AO)\u6765\u8868\u793a\u53d8\u91cf\u5bf9\u8c61\u3002<\/p>\n<p dir=\"auto\">\u6d3b\u52a8\u5bf9\u8c61\u548c\u53d8\u91cf\u5bf9\u8c61\u5176\u5b9e\u662f\u4e00\u4e2a\u4e1c\u897f\uff0c\u53ea\u662f\u53d8\u91cf\u5bf9\u8c61\u662f\u89c4\u8303\u4e0a\u7684\u6216\u8005\u8bf4\u662f\u5f15\u64ce\u5b9e\u73b0\u4e0a\u7684\uff0c\u4e0d\u53ef\u5728 JavaScript \u73af\u5883\u4e2d\u8bbf\u95ee\uff0c\u53ea\u6709\u5230\u5f53\u8fdb\u5165\u4e00\u4e2a\u6267\u884c\u4e0a\u4e0b\u6587\u4e2d\uff0c\u8fd9\u4e2a\u6267\u884c\u4e0a\u4e0b\u6587\u7684\u53d8\u91cf\u5bf9\u8c61\u624d\u4f1a\u88ab\u6fc0\u6d3b\uff0c\u6240\u4ee5\u624d\u53eb activation object \u5450\uff0c\u800c\u53ea\u6709\u88ab\u6fc0\u6d3b\u7684\u53d8\u91cf\u5bf9\u8c61\uff0c\u4e5f\u5c31\u662f\u6d3b\u52a8\u5bf9\u8c61\u4e0a\u7684\u5404\u79cd\u5c5e\u6027\u624d\u80fd\u88ab\u8bbf\u95ee\u3002<\/p>\n<p dir=\"auto\">\u6d3b\u52a8\u5bf9\u8c61\u662f\u5728\u8fdb\u5165\u51fd\u6570\u4e0a\u4e0b\u6587\u65f6\u523b\u88ab\u521b\u5efa\u7684\uff0c\u5b83\u901a\u8fc7\u51fd\u6570\u7684 arguments \u5c5e\u6027\u521d\u59cb\u5316\u3002arguments \u5c5e\u6027\u503c\u662f Arguments \u5bf9\u8c61\u3002<\/p>\n<h2 dir=\"auto\">\u6267\u884c\u8fc7\u7a0b<\/h2>\n<p dir=\"auto\">\u6267\u884c\u4e0a\u4e0b\u6587\u7684\u4ee3\u7801\u4f1a\u5206\u6210\u4e24\u4e2a\u9636\u6bb5\u8fdb\u884c\u5904\u7406\uff1a\u5206\u6790\u548c\u6267\u884c\uff0c\u6211\u4eec\u4e5f\u53ef\u4ee5\u53eb\u505a\uff1a<\/p>\n<ol dir=\"auto\">\n<li>\u8fdb\u5165\u6267\u884c\u4e0a\u4e0b\u6587<\/li>\n<li>\u4ee3\u7801\u6267\u884c<\/li>\n<\/ol>\n<h3 dir=\"auto\">\u8fdb\u5165\u6267\u884c\u4e0a\u4e0b\u6587<\/h3>\n<p dir=\"auto\">\u5f53\u8fdb\u5165\u6267\u884c\u4e0a\u4e0b\u6587\u65f6\uff0c\u8fd9\u65f6\u5019\u8fd8\u6ca1\u6709\u6267\u884c\u4ee3\u7801\uff0c<\/p>\n<p dir=\"auto\">\u53d8\u91cf\u5bf9\u8c61\u4f1a\u5305\u62ec\uff1a<\/p>\n<ol dir=\"auto\">\n<li>\n<p dir=\"auto\">\u51fd\u6570\u7684\u6240\u6709\u5f62\u53c2 (\u5982\u679c\u662f\u51fd\u6570\u4e0a\u4e0b\u6587)<\/p>\n<ul dir=\"auto\">\n<li>\u7531\u540d\u79f0\u548c\u5bf9\u5e94\u503c\u7ec4\u6210\u7684\u4e00\u4e2a\u53d8\u91cf\u5bf9\u8c61\u7684\u5c5e\u6027\u88ab\u521b\u5efa<\/li>\n<li>\u6ca1\u6709\u5b9e\u53c2\uff0c\u5c5e\u6027\u503c\u8bbe\u4e3a undefined<\/li>\n<\/ul>\n<\/li>\n<li>\n<p dir=\"auto\">\u51fd\u6570\u58f0\u660e<\/p>\n<ul dir=\"auto\">\n<li>\u7531\u540d\u79f0\u548c\u5bf9\u5e94\u503c\uff08\u51fd\u6570\u5bf9\u8c61(function-object)\uff09\u7ec4\u6210\u4e00\u4e2a\u53d8\u91cf\u5bf9\u8c61\u7684\u5c5e\u6027\u88ab\u521b\u5efa<\/li>\n<li>\u5982\u679c\u53d8\u91cf\u5bf9\u8c61\u5df2\u7ecf\u5b58\u5728\u76f8\u540c\u540d\u79f0\u7684\u5c5e\u6027\uff0c\u5219\u5b8c\u5168\u66ff\u6362\u8fd9\u4e2a\u5c5e\u6027<\/li>\n<\/ul>\n<\/li>\n<li>\n<p dir=\"auto\">\u53d8\u91cf\u58f0\u660e<\/p>\n<ul dir=\"auto\">\n<li>\u7531\u540d\u79f0\u548c\u5bf9\u5e94\u503c\uff08undefined\uff09\u7ec4\u6210\u4e00\u4e2a\u53d8\u91cf\u5bf9\u8c61\u7684\u5c5e\u6027\u88ab\u521b\u5efa\uff1b<\/li>\n<li>\u5982\u679c\u53d8\u91cf\u540d\u79f0\u8ddf\u5df2\u7ecf\u58f0\u660e\u7684\u5f62\u5f0f\u53c2\u6570\u6216\u51fd\u6570\u76f8\u540c\uff0c\u5219\u53d8\u91cf\u58f0\u660e\u4e0d\u4f1a\u5e72\u6270\u5df2\u7ecf\u5b58\u5728\u7684\u8fd9\u7c7b\u5c5e\u6027<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n<p dir=\"auto\">\u4e3e\u4e2a\u4f8b\u5b50\uff1a<\/p>\n<div class=\"highlight highlight-source-js notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content=\"function foo(a) {\n  var b = 2;\n  function c() {}\n  var d = function() {};\n\n  b = 3;\n\n}\n\nfoo(1);\"><\/p>\n<pre class=\"notranslate\"><span class=\"pl-k\">function<\/span> <span class=\"pl-en\">foo<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">a<\/span><span class=\"pl-kos\">)<\/span> <span class=\"pl-kos\">{<\/span>\n  <span class=\"pl-k\">var<\/span> <span class=\"pl-s1\">b<\/span> <span class=\"pl-c1\">=<\/span> <span class=\"pl-c1\">2<\/span><span class=\"pl-kos\">;<\/span>\n  <span class=\"pl-k\">function<\/span> <span class=\"pl-en\">c<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span> <span class=\"pl-kos\">{<\/span><span class=\"pl-kos\">}<\/span>\n  <span class=\"pl-k\">var<\/span> <span class=\"pl-en\">d<\/span> <span class=\"pl-c1\">=<\/span> <span class=\"pl-k\">function<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span> <span class=\"pl-kos\">{<\/span><span class=\"pl-kos\">}<\/span><span class=\"pl-kos\">;<\/span>\n\n  <span class=\"pl-s1\">b<\/span> <span class=\"pl-c1\">=<\/span> <span class=\"pl-c1\">3<\/span><span class=\"pl-kos\">;<\/span>\n\n<span class=\"pl-kos\">}<\/span>\n\n<span class=\"pl-en\">foo<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-c1\">1<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span><\/pre>\n<\/div>\n<p dir=\"auto\">\u5728\u8fdb\u5165\u6267\u884c\u4e0a\u4e0b\u6587\u540e\uff0c\u8fd9\u65f6\u5019\u7684 AO \u662f\uff1a<\/p>\n<div class=\"highlight highlight-source-js notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content=\"AO = {\n    arguments: {\n        0: 1,\n        length: 1\n    },\n    a: 1,\n    b: undefined,\n    c: reference to function c(){},\n    d: undefined\n}\"><\/p>\n<pre class=\"notranslate\"><span class=\"pl-c1\">AO<\/span> <span class=\"pl-c1\">=<\/span> <span class=\"pl-kos\">{<\/span>\n    <span class=\"pl-c1\">arguments<\/span>: <span class=\"pl-kos\">{<\/span>\n        <span class=\"pl-c1\">0<\/span>: <span class=\"pl-c1\">1<\/span><span class=\"pl-kos\">,<\/span>\n        <span class=\"pl-c1\">length<\/span>: <span class=\"pl-c1\">1<\/span>\n    <span class=\"pl-kos\">}<\/span><span class=\"pl-kos\">,<\/span>\n    <span class=\"pl-c1\">a<\/span>: <span class=\"pl-c1\">1<\/span><span class=\"pl-kos\">,<\/span>\n    <span class=\"pl-c1\">b<\/span>: <span class=\"pl-c1\">undefined<\/span><span class=\"pl-kos\">,<\/span>\n    <span class=\"pl-en\">c<\/span>: <span class=\"pl-s1\">reference<\/span> <span class=\"pl-s1\">to<\/span> <span class=\"pl-k\">function<\/span> <span class=\"pl-en\">c<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">{<\/span><span class=\"pl-kos\">}<\/span><span class=\"pl-kos\">,<\/span>\n    <span class=\"pl-c1\">d<\/span>: <span class=\"pl-c1\">undefined<\/span>\n<span class=\"pl-kos\">}<\/span><\/pre>\n<\/div>\n<h3 dir=\"auto\">\u4ee3\u7801\u6267\u884c<\/h3>\n<p dir=\"auto\">\u5728\u4ee3\u7801\u6267\u884c\u9636\u6bb5\uff0c\u4f1a\u987a\u5e8f\u6267\u884c\u4ee3\u7801\uff0c\u6839\u636e\u4ee3\u7801\uff0c\u4fee\u6539\u53d8\u91cf\u5bf9\u8c61\u7684\u503c<\/p>\n<p dir=\"auto\">\u8fd8\u662f\u4e0a\u9762\u7684\u4f8b\u5b50\uff0c\u5f53\u4ee3\u7801\u6267\u884c\u5b8c\u540e\uff0c\u8fd9\u65f6\u5019\u7684 AO \u662f\uff1a<\/p>\n<div class=\"highlight highlight-source-js notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content='AO = {\n    arguments: {\n        0: 1,\n        length: 1\n    },\n    a: 1,\n    b: 3,\n    c: reference to function c(){},\n    d: reference to FunctionExpression \"d\"\n}'><\/p>\n<pre class=\"notranslate\"><span class=\"pl-c1\">AO<\/span> <span class=\"pl-c1\">=<\/span> <span class=\"pl-kos\">{<\/span>\n    <span class=\"pl-c1\">arguments<\/span>: <span class=\"pl-kos\">{<\/span>\n        <span class=\"pl-c1\">0<\/span>: <span class=\"pl-c1\">1<\/span><span class=\"pl-kos\">,<\/span>\n        <span class=\"pl-c1\">length<\/span>: <span class=\"pl-c1\">1<\/span>\n    <span class=\"pl-kos\">}<\/span><span class=\"pl-kos\">,<\/span>\n    <span class=\"pl-c1\">a<\/span>: <span class=\"pl-c1\">1<\/span><span class=\"pl-kos\">,<\/span>\n    <span class=\"pl-c1\">b<\/span>: <span class=\"pl-c1\">3<\/span><span class=\"pl-kos\">,<\/span>\n    <span class=\"pl-en\">c<\/span>: <span class=\"pl-s1\">reference<\/span> <span class=\"pl-s1\">to<\/span> <span class=\"pl-k\">function<\/span> <span class=\"pl-en\">c<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">{<\/span><span class=\"pl-kos\">}<\/span><span class=\"pl-kos\">,<\/span>\n    <span class=\"pl-c1\">d<\/span>: <span class=\"pl-s1\">reference<\/span> <span class=\"pl-s1\">to<\/span> <span class=\"pl-v\">FunctionExpression<\/span> <span class=\"pl-s\">\"d\"<\/span>\n<span class=\"pl-kos\">}<\/span><\/pre>\n<\/div>\n<p dir=\"auto\">\u5230\u8fd9\u91cc\u53d8\u91cf\u5bf9\u8c61\u7684\u521b\u5efa\u8fc7\u7a0b\u5c31\u4ecb\u7ecd\u5b8c\u4e86\uff0c\u8ba9\u6211\u4eec\u7b80\u6d01\u7684\u603b\u7ed3\u6211\u4eec\u4e0a\u8ff0\u6240\u8bf4\uff1a<\/p>\n<ol dir=\"auto\">\n<li>\n<p dir=\"auto\">\u5168\u5c40\u4e0a\u4e0b\u6587\u7684\u53d8\u91cf\u5bf9\u8c61\u521d\u59cb\u5316\u662f\u5168\u5c40\u5bf9\u8c61<\/p>\n<\/li>\n<li>\n<p dir=\"auto\">\u51fd\u6570\u4e0a\u4e0b\u6587\u7684\u53d8\u91cf\u5bf9\u8c61\u521d\u59cb\u5316\u53ea\u5305\u62ec Arguments \u5bf9\u8c61<\/p>\n<\/li>\n<li>\n<p dir=\"auto\">\u5728\u8fdb\u5165\u6267\u884c\u4e0a\u4e0b\u6587\u65f6\u4f1a\u7ed9\u53d8\u91cf\u5bf9\u8c61\u6dfb\u52a0\u5f62\u53c2\u3001\u51fd\u6570\u58f0\u660e\u3001\u53d8\u91cf\u58f0\u660e\u7b49\u521d\u59cb\u7684\u5c5e\u6027\u503c<\/p>\n<\/li>\n<li>\n<p dir=\"auto\">\u5728\u4ee3\u7801\u6267\u884c\u9636\u6bb5\uff0c\u4f1a\u518d\u6b21\u4fee\u6539\u53d8\u91cf\u5bf9\u8c61\u7684\u5c5e\u6027\u503c<\/p>\n<\/li>\n<\/ol>\n<h2 dir=\"auto\">\u601d\u8003\u9898<\/h2>\n<p dir=\"auto\">\u6700\u540e\u8ba9\u6211\u4eec\u770b\u51e0\u4e2a\u4f8b\u5b50\uff1a<\/p>\n<p dir=\"auto\">1.\u7b2c\u4e00\u9898<\/p>\n<div class=\"highlight highlight-source-js notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content=\"function foo() {\n    console.log(a);\n    a = 1;\n}\n\nfoo(); \/\/ ???\n\nfunction bar() {\n    a = 1;\n    console.log(a);\n}\nbar(); \/\/ ???\"><\/p>\n<pre class=\"notranslate\"><span class=\"pl-k\">function<\/span> <span class=\"pl-en\">foo<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span> <span class=\"pl-kos\">{<\/span>\n    <span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">a<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n    <span class=\"pl-s1\">a<\/span> <span class=\"pl-c1\">=<\/span> <span class=\"pl-c1\">1<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-kos\">}<\/span>\n\n<span class=\"pl-en\">foo<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span> <span class=\"pl-c\">\/\/ ???<\/span>\n\n<span class=\"pl-k\">function<\/span> <span class=\"pl-en\">bar<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span> <span class=\"pl-kos\">{<\/span>\n    <span class=\"pl-s1\">a<\/span> <span class=\"pl-c1\">=<\/span> <span class=\"pl-c1\">1<\/span><span class=\"pl-kos\">;<\/span>\n    <span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">a<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-kos\">}<\/span>\n<span class=\"pl-en\">bar<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span> <span class=\"pl-c\">\/\/ ???<\/span><\/pre>\n<\/div>\n<p dir=\"auto\">\u7b2c\u4e00\u6bb5\u4f1a\u62a5\u9519\uff1a<code class=\"notranslate\">Uncaught ReferenceError: a is not defined<\/code>\u3002<\/p>\n<p dir=\"auto\">\u7b2c\u4e8c\u6bb5\u4f1a\u6253\u5370\uff1a<code class=\"notranslate\">1<\/code>\u3002<\/p>\n<p dir=\"auto\">\u8fd9\u662f\u56e0\u4e3a\u51fd\u6570\u4e2d\u7684 &#8220;a&#8221; \u5e76\u6ca1\u6709\u901a\u8fc7 var \u5173\u952e\u5b57\u58f0\u660e\uff0c\u6240\u6709\u4e0d\u4f1a\u88ab\u5b58\u653e\u5728 AO \u4e2d\u3002<\/p>\n<p dir=\"auto\">\u7b2c\u4e00\u6bb5\u6267\u884c console \u7684\u65f6\u5019\uff0c AO \u7684\u503c\u662f\uff1a<\/p>\n<div class=\"highlight highlight-source-js notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content=\"AO = {\n    arguments: {\n        length: 0\n    }\n}\"><\/p>\n<pre class=\"notranslate\"><span class=\"pl-c1\">AO<\/span> <span class=\"pl-c1\">=<\/span> <span class=\"pl-kos\">{<\/span>\n    <span class=\"pl-c1\">arguments<\/span>: <span class=\"pl-kos\">{<\/span>\n        <span class=\"pl-c1\">length<\/span>: <span class=\"pl-c1\">0<\/span>\n    <span class=\"pl-kos\">}<\/span>\n<span class=\"pl-kos\">}<\/span><\/pre>\n<\/div>\n<p dir=\"auto\">\u6ca1\u6709 a \u7684\u503c\uff0c\u7136\u540e\u5c31\u4f1a\u5230\u5168\u5c40\u53bb\u627e\uff0c\u5168\u5c40\u4e5f\u6ca1\u6709\uff0c\u6240\u4ee5\u4f1a\u62a5\u9519\u3002<\/p>\n<p dir=\"auto\">\u5f53\u7b2c\u4e8c\u6bb5\u6267\u884c console \u7684\u65f6\u5019\uff0c\u5168\u5c40\u5bf9\u8c61\u5df2\u7ecf\u88ab\u8d4b\u4e88\u4e86 a \u5c5e\u6027\uff0c\u8fd9\u65f6\u5019\u5c31\u53ef\u4ee5\u4ece\u5168\u5c40\u627e\u5230 a \u7684\u503c\uff0c\u6240\u4ee5\u4f1a\u6253\u5370 1\u3002<\/p>\n<p dir=\"auto\">2.\u7b2c\u4e8c\u9898<\/p>\n<div class=\"highlight highlight-source-js notranslate position-relative overflow-auto\" dir=\"auto\" data-snippet-clipboard-copy-content='console.log(foo);\n\nfunction foo(){\n    console.log(\"foo\");\n}\n\nvar foo = 1;'><\/p>\n<pre class=\"notranslate\"><span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s1\">foo<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n\n<span class=\"pl-k\">function<\/span> <span class=\"pl-en\">foo<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">{<\/span>\n    <span class=\"pl-smi\">console<\/span><span class=\"pl-kos\">.<\/span><span class=\"pl-en\">log<\/span><span class=\"pl-kos\">(<\/span><span class=\"pl-s\">\"foo\"<\/span><span class=\"pl-kos\">)<\/span><span class=\"pl-kos\">;<\/span>\n<span class=\"pl-kos\">}<\/span>\n\n<span class=\"pl-k\">var<\/span> <span class=\"pl-s1\">foo<\/span> <span class=\"pl-c1\">=<\/span> <span class=\"pl-c1\">1<\/span><span class=\"pl-kos\">;<\/span><\/pre>\n<\/div>\n<p dir=\"auto\">\u4f1a\u6253\u5370\u51fd\u6570\uff0c\u800c\u4e0d\u662f undefined \u3002<\/p>\n<p dir=\"auto\">\u8fd9\u662f\u56e0\u4e3a\u5728\u8fdb\u5165\u6267\u884c\u4e0a\u4e0b\u6587\u65f6\uff0c\u9996\u5148\u4f1a\u5904\u7406\u51fd\u6570\u58f0\u660e\uff0c\u5176\u6b21\u4f1a\u5904\u7406\u53d8\u91cf\u58f0\u660e\uff0c\u5982\u679c\u53d8\u91cf\u540d\u79f0\u8ddf\u5df2\u7ecf\u58f0\u660e\u7684\u5f62\u5f0f\u53c2\u6570\u6216\u51fd\u6570\u76f8\u540c\uff0c\u5219\u53d8\u91cf\u58f0\u660e\u4e0d\u4f1a\u5e72\u6270\u5df2\u7ecf\u5b58\u5728\u7684\u8fd9\u7c7b\u5c5e\u6027\u3002<\/p>\n<h2 dir=\"auto\">\u4e0b\u4e00\u7bc7\u6587\u7ae0<\/h2>\n<p dir=\"auto\"><a href=\"https:\/\/github.com\/mqyqingfeng\/Blog\/issues\/6\" data-hovercard-type=\"issue\" data-hovercard-url=\"\/mqyqingfeng\/Blog\/issues\/6\/hovercard\">\u300aJavaScript\u6df1\u5165\u4e4b\u4f5c\u7528\u57df\u94fe\u300b<\/a><\/p>\n<h2 dir=\"auto\">\u672c\u6587\u76f8\u5173\u94fe\u63a5<\/h2>\n<p dir=\"auto\"><a href=\"https:\/\/github.com\/mqyqingfeng\/Blog\/issues\/4\" data-hovercard-type=\"issue\" data-hovercard-url=\"\/mqyqingfeng\/Blog\/issues\/4\/hovercard\">\u300aJavaScript\u6df1\u5165\u4e4b\u6267\u884c\u4e0a\u4e0b\u6587\u6808\u300b<\/a><\/p>\n<h2 dir=\"auto\">\u6df1\u5165\u7cfb\u5217<\/h2>\n<p dir=\"auto\">JavaScript\u6df1\u5165\u7cfb\u5217\u76ee\u5f55\u5730\u5740\uff1a<a href=\"https:\/\/github.com\/mqyqingfeng\/Blog\">https:\/\/github.com\/mqyqingfeng\/Blog<\/a>\u3002<\/p>\n<p dir=\"auto\">JavaScript\u6df1\u5165\u7cfb\u5217\u9884\u8ba1\u5199\u5341\u4e94\u7bc7\u5de6\u53f3\uff0c\u65e8\u5728\u5e2e\u5927\u5bb6\u634b\u987aJavaScript\u5e95\u5c42\u77e5\u8bc6\uff0c\u91cd\u70b9\u8bb2\u89e3\u5982\u539f\u578b\u3001\u4f5c\u7528\u57df\u3001\u6267\u884c\u4e0a\u4e0b\u6587\u3001\u53d8\u91cf\u5bf9\u8c61\u3001this\u3001\u95ed\u5305\u3001\u6309\u503c\u4f20\u9012\u3001call\u3001apply\u3001bind\u3001new\u3001\u7ee7\u627f\u7b49\u96be\u70b9\u6982\u5ff5\u3002<\/p>\n<p dir=\"auto\">\u5982\u679c\u6709\u9519\u8bef\u6216\u8005\u4e0d\u4e25\u8c28\u7684\u5730\u65b9\uff0c\u8bf7\u52a1\u5fc5\u7ed9\u4e88\u6307\u6b63\uff0c\u5341\u5206\u611f\u8c22\u3002\u5982\u679c\u559c\u6b22\u6216\u8005\u6709\u6240\u542f\u53d1\uff0c\u6b22\u8fcestar\uff0c\u5bf9\u4f5c\u8005\u4e5f\u662f\u4e00\u79cd\u9f13\u52b1\u3002<\/p>\n<\/td>\n<p>\u6587\u7ae0\u8f6c\u8f7d\u81ea<a href='https:\/\/github.com\/mqyqingfeng\/Blog\/issues\/5'>https:\/\/github.com\/mqyqingfeng\/Blog\/issues\/5<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u524d\u8a00 \u5728\u4e0a\u7bc7\u300aJavaScript\u6df1\u5165\u4e4b\u6267\u884c\u4e0a\u4e0b\u6587\u6808\u300b\u4e2d\u8bb2\u5230\uff0c\u5f53 JavaScript \u4ee3\u7801\u6267\u884c\u4e00\u6bb5\u53ef\u6267\u884c\u4ee3\u7801(executable code)\u65f6\uff0c\u4f1a\u521b\u5efa\u5bf9\u5e94\u7684&#8230;<\/p>\n<p class=\"read-more\"><a class=\"btn btn-default\" href=\"https:\/\/www.lccc.top\/?p=1389\"> Read More<span class=\"screen-reader-text\">  Read More<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-1389","post","type-post","status-publish","format-standard","hentry","category-learn"],"_links":{"self":[{"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts\/1389"}],"collection":[{"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1389"}],"version-history":[{"count":1,"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts\/1389\/revisions"}],"predecessor-version":[{"id":1492,"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts\/1389\/revisions\/1492"}],"wp:attachment":[{"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1389"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1389"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1389"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}