{"id":743,"date":"2011-08-31T02:27:11","date_gmt":"2011-08-30T18:27:11","guid":{"rendered":""},"modified":"2014-03-11T22:39:34","modified_gmt":"2014-03-11T14:39:34","slug":"javascript%e5%86%85%e5%ad%98%e6%b3%84%e6%bc%8f%e4%b9%8b%e9%97%ad%e5%8c%85","status":"publish","type":"post","link":"http:\/\/www.xiaoyebailong.com\/index.php\/2011\/08\/31\/743.htm","title":{"rendered":"JavaScript\u5185\u5b58\u6cc4\u6f0f\u4e4b\u95ed\u5305"},"content":{"rendered":"
\n

\u95ed\u5305\uff1a<\/strong><\/p>\n

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\u5982\uff1a<\/p>\n

function a(){
\nvar i=0;
\nfunction b(){
\nalert(++i);
\n}
\nreturn b;
\n}
\nvar c = a();
\nc();
\n\u8fd9\u6bb5\u4ee3\u7801\u6709\u4e24\u4e2a\u7279\u70b9\uff1a
\n1\u3001\u51fd\u6570b\u5d4c\u5957\u5728\u51fd\u6570a\u5185\u90e8\uff1b
\n2\u3001\u51fd\u6570a\u8fd4\u56de\u51fd\u6570b\u3002
\n\u8fd9\u6837\u5728\u6267\u884c\u5b8cvar c=a()\u540e\uff0c\u53d8\u91cfc\u5b9e\u9645\u4e0a\u662f\u6307\u5411\u4e86\u51fd\u6570b\uff0c\u518d\u6267\u884cc()\u540e\u5c31\u4f1a\u5f39\u51fa\u4e00\u4e2a\u7a97\u53e3\u663e\u793ai\u7684\u503c(\u7b2c\u4e00\u6b21\u4e3a1)\u3002\u8fd9\u6bb5\u4ee3\u7801\u5176\u5b9e\u5c31\u521b\u5efa\u4e86\u4e00\u4e2a\u95ed\u5305\uff0c\u4e3a\u4ec0\u4e48\uff1f\u56e0\u4e3a\u51fd\u6570a\u5916\u7684\u53d8\u91cfc\u5f15\u7528\u4e86\u51fd\u6570a\u5185\u7684\u51fd\u6570b\uff0c\u5c31\u662f\u8bf4\uff1a<\/p>\n

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\n\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c\u7531\u4e8e\u95ed\u5305\u7684\u5b58\u5728\u4f7f\u5f97\u51fd\u6570a\u8fd4\u56de\u540e\uff0ca\u4e2d\u7684i\u59cb\u7ec8\u5b58\u5728\uff0c\u8fd9\u6837\u6bcf\u6b21\u6267\u884cc()\uff0ci\u90fd\u662f\u81ea\u52a01\u540ealert\u51fai\u7684\u503c\u3002<\/p>\n

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\u4e09\u3001\u95ed\u5305\u5185\u7684\u5fae\u89c2\u4e16\u754c
\n\u5982\u679c\u8981\u66f4\u52a0\u6df1\u5165\u7684\u4e86\u89e3\u95ed\u5305\u4ee5\u53ca\u51fd\u6570a\u548c\u5d4c\u5957\u51fd\u6570b\u7684\u5173\u7cfb\uff0c\u6211\u4eec\u9700\u8981\u5f15\u5165\u53e6\u5916\u51e0\u4e2a\u6982\u5ff5\uff1a\u51fd\u6570\u7684\u6267\u884c\u73af\u5883(excution context)\u3001\u6d3b\u52a8\u5bf9\u8c61(call object)\u3001\u4f5c\u7528\u57df(scope)\u3001\u4f5c\u7528\u57df\u94fe(scope chain)\u3002\u4ee5\u51fd\u6570a\u4ece\u5b9a\u4e49\u5230\u6267\u884c\u7684\u8fc7\u7a0b\u4e3a\u4f8b\u9610\u8ff0\u8fd9\u51e0\u4e2a\u6982\u5ff5\u3002<\/p>\n

1\u3001\u5f53\u5b9a\u4e49\u51fd\u6570a\u7684\u65f6\u5019\uff0cjs\u89e3\u91ca\u5668\u4f1a\u5c06\u51fd\u6570a\u7684\u4f5c\u7528\u57df\u94fe(scope chain)\u8bbe\u7f6e\u4e3a\u5b9a\u4e49a\u65f6a\u6240\u5728\u7684“\u73af\u5883”\uff0c\u5982\u679ca\u662f\u4e00\u4e2a\u5168\u5c40\u51fd\u6570\uff0c\u5219scope chain\u4e2d\u53ea\u6709window\u5bf9\u8c61\u3002
\n2\u3001\u5f53\u51fd\u6570a\u6267\u884c\u7684\u65f6\u5019\uff0ca\u4f1a\u8fdb\u5165\u76f8\u5e94\u7684\u6267\u884c\u73af\u5883(excution context)\u3002
\n3\u3001\u5728\u521b\u5efa\u6267\u884c\u73af\u5883\u7684\u8fc7\u7a0b\u4e2d\uff0c\u9996\u5148\u4f1a\u4e3aa\u6dfb\u52a0\u4e00\u4e2ascope\u5c5e\u6027\uff0c\u5373a\u7684\u4f5c\u7528\u57df\uff0c\u5176\u503c\u5c31\u4e3a\u7b2c1\u6b65\u4e2d\u7684scope chain\u3002\u5373a.scope=a\u7684\u4f5c\u7528\u57df\u94fe\u3002
\n4\u3001\u7136\u540e\u6267\u884c\u73af\u5883\u4f1a\u521b\u5efa\u4e00\u4e2a\u6d3b\u52a8\u5bf9\u8c61(call object)\u3002\u6d3b\u52a8\u5bf9\u8c61\u4e5f\u662f\u4e00\u4e2a\u62e5\u6709\u5c5e\u6027\u7684\u5bf9\u8c61\uff0c\u4f46\u5b83\u4e0d\u5177\u6709\u539f\u578b\u800c\u4e14\u4e0d\u80fd\u901a\u8fc7JavaScript\u4ee3\u7801\u76f4\u63a5\u8bbf\u95ee\u3002\u521b\u5efa\u5b8c\u6d3b\u52a8\u5bf9\u8c61\u540e\uff0c\u628a\u6d3b\u52a8\u5bf9\u8c61\u6dfb\u52a0\u5230a\u7684\u4f5c\u7528\u57df\u94fe\u7684\u6700\u9876\u7aef\u3002\u6b64\u65f6a\u7684\u4f5c\u7528\u57df\u94fe\u5305\u542b\u4e86\u4e24\u4e2a\u5bf9\u8c61\uff1aa\u7684\u6d3b\u52a8\u5bf9\u8c61\u548cwindow\u5bf9\u8c61\u3002
\n5\u3001\u4e0b\u4e00\u6b65\u662f\u5728\u6d3b\u52a8\u5bf9\u8c61\u4e0a\u6dfb\u52a0\u4e00\u4e2aarguments\u5c5e\u6027\uff0c\u5b83\u4fdd\u5b58\u7740\u8c03\u7528\u51fd\u6570a\u65f6\u6240\u4f20\u9012\u7684\u53c2\u6570\u3002
\n6\u3001\u6700\u540e\u628a\u6240\u6709\u51fd\u6570a\u7684\u5f62\u53c2\u548c\u5185\u90e8\u7684\u51fd\u6570b\u7684\u5f15\u7528\u4e5f\u6dfb\u52a0\u5230a\u7684\u6d3b\u52a8\u5bf9\u8c61\u4e0a\u3002\u5728\u8fd9\u4e00\u6b65\u4e2d\uff0c\u5b8c\u6210\u4e86\u51fd\u6570b\u7684\u7684\u5b9a\u4e49\uff0c\u56e0\u6b64\u5982\u540c\u7b2c3\u6b65\uff0c\u51fd\u6570b\u7684\u4f5c\u7528\u57df\u94fe\u88ab\u8bbe\u7f6e\u4e3ab\u6240\u88ab\u5b9a\u4e49\u7684\u73af\u5883\uff0c\u5373a\u7684\u4f5c\u7528\u57df\u3002<\/p>\n

\u5230\u6b64\uff0c\u6574\u4e2a\u51fd\u6570a\u4ece\u5b9a\u4e49\u5230\u6267\u884c\u7684\u6b65\u9aa4\u5c31\u5b8c\u6210\u4e86\u3002\u6b64\u65f6a\u8fd4\u56de\u51fd\u6570b\u7684\u5f15\u7528\u7ed9c\uff0c\u53c8\u51fd\u6570b\u7684\u4f5c\u7528\u57df\u94fe\u5305\u542b\u4e86\u5bf9\u51fd\u6570a\u7684\u6d3b\u52a8\u5bf9\u8c61\u7684\u5f15\u7528\uff0c\u4e5f\u5c31\u662f\u8bf4b\u53ef\u4ee5\u8bbf\u95ee\u5230a\u4e2d\u5b9a\u4e49\u7684\u6240\u6709\u53d8\u91cf\u548c\u51fd\u6570\u3002\u51fd\u6570b\u88abc\u5f15\u7528\uff0c\u51fd\u6570b\u53c8\u4f9d\u8d56\u51fd\u6570a\uff0c\u56e0\u6b64\u51fd\u6570a\u5728\u8fd4\u56de\u540e\u4e0d\u4f1a\u88abGC\u56de\u6536\u3002<\/p>\n

\u5f53\u51fd\u6570b\u6267\u884c\u7684\u65f6\u5019\u4ea6\u4f1a\u50cf\u4ee5\u4e0a\u6b65\u9aa4\u4e00\u6837\u3002\u56e0\u6b64\uff0c\u6267\u884c\u65f6b\u7684\u4f5c\u7528\u57df\u94fe\u5305\u542b\u4e863\u4e2a\u5bf9\u8c61\uff1ab\u7684\u6d3b\u52a8\u5bf9\u8c61\u3001a\u7684\u6d3b\u52a8\u5bf9\u8c61\u548cwindow\u5bf9\u8c61.<\/p>\n

\u5f53\u5728\u51fd\u6570b\u4e2d\u8bbf\u95ee\u4e00\u4e2a\u53d8\u91cf\u7684\u65f6\u5019\uff0c\u641c\u7d22\u987a\u5e8f\u662f\u5148\u641c\u7d22\u81ea\u8eab\u7684\u6d3b\u52a8\u5bf9\u8c61\uff0c\u5982\u679c\u5b58\u5728\u5219\u8fd4\u56de\uff0c\u5982\u679c\u4e0d\u5b58\u5728\u5c06\u7ee7\u7eed\u641c\u7d22\u51fd\u6570a\u7684\u6d3b\u52a8\u5bf9\u8c61\uff0c\u4f9d\u6b21\u67e5\u627e\uff0c\u76f4\u5230\u627e\u5230\u4e3a\u6b62\u3002\u5982\u679c\u6574\u4e2a\u4f5c\u7528\u57df\u94fe\u4e0a\u90fd\u65e0\u6cd5\u627e\u5230\uff0c\u5219\u8fd4\u56deundefined\u3002\u5982\u679c\u51fd\u6570b\u5b58\u5728prototype\u539f\u578b\u5bf9\u8c61\uff0c\u5219\u5728\u67e5\u627e\u5b8c\u81ea\u8eab\u7684\u6d3b\u52a8\u5bf9\u8c61 \u540e\u5148\u67e5\u627e\u81ea\u8eab\u7684\u539f\u578b\u5bf9\u8c61\uff0c\u518d\u7ee7\u7eed\u67e5\u627e\u3002\u8fd9\u5c31\u662fJavascript\u4e2d\u7684\u53d8\u91cf\u67e5\u627e\u673a\u5236\u3002<\/p>\n

\u56db\u3001\u95ed\u5305\u7684\u5e94\u7528\u573a\u666f
\n1\u3001\u4fdd\u62a4\u51fd\u6570\u5185\u7684\u53d8\u91cf\u5b89\u5168\u3002\u4ee5\u6700\u5f00\u59cb\u7684\u4f8b\u5b50\u4e3a\u4f8b\uff0c\u51fd\u6570a\u4e2di\u53ea\u6709\u51fd\u6570b\u624d\u80fd\u8bbf\u95ee\uff0c\u800c\u65e0\u6cd5\u901a\u8fc7\u5176\u4ed6\u9014\u5f84\u8bbf\u95ee\u5230\uff0c\u56e0\u6b64\u4fdd\u62a4\u4e86i\u7684\u5b89\u5168\u6027\u3002
\n2\u3001\u5728\u5185\u5b58\u4e2d\u7ef4\u6301\u4e00\u4e2a\u53d8\u91cf\u3002\u4f9d\u7136\u5982\u524d\u4f8b\uff0c\u7531\u4e8e\u95ed\u5305\uff0c\u51fd\u6570a\u4e2di\u7684\u4e00\u76f4\u5b58\u5728\u4e8e\u5185\u5b58\u4e2d\uff0c\u56e0\u6b64\u6bcf\u6b21\u6267\u884cc()\uff0c\u90fd\u4f1a\u7ed9i\u81ea\u52a01\u3002
\n\u4ee5\u4e0a\u4e24\u70b9\u662f\u95ed\u5305\u6700\u57fa\u672c\u7684\u5e94\u7528\u573a\u666f\uff0c\u5f88\u591a\u7ecf\u5178\u6848\u4f8b\u90fd\u6e90\u4e8e\u6b64\u3002<\/p>\n

\u4e94\u3001Javascript\u7684\u5783\u573e\u56de\u6536\u673a\u5236
\n\u5728Javascript\u4e2d\uff0c\u5982\u679c\u4e00\u4e2a\u5bf9\u8c61\u4e0d\u518d\u88ab\u5f15\u7528\uff0c\u90a3\u4e48\u8fd9\u4e2a\u5bf9\u8c61\u5c31\u4f1a\u88abGC\u56de\u6536\u3002\u5982\u679c\u4e24\u4e2a\u5bf9\u8c61\u4e92\u76f8\u5f15\u7528\uff0c\u800c\u4e0d\u518d\u88ab\u7b2c3\u8005\u6240\u5f15\u7528\uff0c\u90a3\u4e48\u8fd9\u4e24\u4e2a\u4e92\u76f8\u5f15\u7528\u7684\u5bf9\u8c61\u4e5f\u4f1a\u88ab\u56de\u6536\u3002\u56e0\u4e3a\u51fd\u6570a\u88abb\u5f15\u7528\uff0cb\u53c8\u88aba\u5916\u7684c\u5f15\u7528\uff0c\u8fd9\u5c31\u662f\u4e3a\u4ec0\u4e48\u51fd\u6570a\u6267\u884c\u540e\u4e0d\u4f1a\u88ab\u56de\u6536\u7684\u539f\u56e0\u3002<\/p>\n

IE\u4e2d\u7684\u5185\u5b58\u6cc4\u6f0f-\u95ed\u5305<\/strong>\uff1a\uff08\u8fd9\u91cc\u6307\u4e3e\u4e2a\u7b80\u5355\u7684\u4f8b\u5b50\uff09<\/p>\n

1\u3001 \u95ee\u9898\u63cf\u8ff0\uff1a<\/p>\n

function<\/span> init(){
\n        <\/span>var<\/span> elem <\/span>=<\/span> document.getElementByid( <\/span>‘<\/span>id<\/span>‘<\/span> );
\n         elem.onclick <\/span>=<\/span> <\/span>function<\/span>(){
\n             alert(<\/span>‘<\/span>rain-man<\/span>‘<\/span>);
\n            <\/span>\/\/<\/span>\u8fd9\u91cc\u5f15\u7528\u4e86elem\u5143\u7d20<\/span>
\n<\/span>         };
\n     }
\nElem\u5f15\u7528\u4e86\u5b83\u7684click\u4e8b\u4ef6\u7684\u76d1\u542c\u51fd\u6570\uff0c\u540c\u6837\u8be5\u51fd\u6570\u901a\u8fc7\u5176\u4f5c\u7528\u57df\u94fe\u4e5f\u5f15\u7528\u56de\u4e86elem\u5143\u7d20\u3002\u8fd9\u6837\u5728IE\u4e2d\u5373\u4f7f\u79bb\u5f00\u5f53\u524d\u9875\u9762\u4e5f\u4e0d\u4f1a\u91ca\u653e\u8fd9\u4e9b\u5faa\u73af\u5f15\u7528\u3002<\/span><\/p>\n

2\u3001\u89e3\u51b3\u65b9\u6cd5\uff1a<\/span><\/p>\n

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    window.onunload =<\/span> <\/span>function<\/span>(){
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