{"id":3248,"date":"2021-05-19T22:27:46","date_gmt":"2021-05-19T14:27:46","guid":{"rendered":"http:\/\/www.yuguoxy.com\/geekhome\/?p=3248"},"modified":"2026-08-18T12:35:34","modified_gmt":"2026-08-18T04:35:34","slug":"javascript%e5%85%a8%e5%b1%80%e5%8f%98%e9%87%8f%e4%b8%8e%e5%b1%80%e9%83%a8%e5%8f%98%e9%87%8f","status":"publish","type":"post","link":"https:\/\/ai.zhousir.top\/?p=3248","title":{"rendered":"JavaScript\u5168\u5c40\u53d8\u91cf\u4e0e\u5c40\u90e8\u53d8\u91cf"},"content":{"rendered":"
\n

\u8c08 JavaScript \u5168\u5c40\u53d8\u91cf\u548c\u5c40\u90e8\u53d8\u91cf\u4e4b\u524d\uff0c\u5148\u8bb0\u4f4f\u4e09\u4ef6\u4e8b\uff1a\u67e5\u627e\u53d8\u91cf\u8d70\u7684\u662f\u4f5c\u7528\u57df\u94fe<\/strong>\uff1b\u7528 var<\/code> \u65f6\u6ca1\u6709\u5757\u7ea7\u4f5c\u7528\u57df<\/strong>\uff1b\u51fd\u6570\u91cc\u58f0\u660e\u7684\u53d8\u91cf\u5728\u6574\u4e2a\u51fd\u6570\u4f53\u90fd\u6709\u6548\u3002<\/p>\n

ES6 \u7684 let<\/code> \/ const<\/code> \u624d\u771f\u6b63\u6709\u5757\u7ea7\u4f5c\u7528\u57df\u3002 \u4e0b\u6587\u4f8b\u5b50\u5168\u90e8\u6cbf\u7528\u539f\u6587\u7684 var<\/code>\uff0c\u8fd9\u662f\u9762\u8bd5\u91cc\u4ecd\u7ecf\u5e38\u88ab\u8ffd\u95ee\u7684\u7ecf\u5178\u884c\u4e3a\u3002<\/p>\n

\u4e00\u3001\u4f5c\u7528\u57df\u94fe<\/h2>\n

inner<\/code> \u91cc\u7684 alert(rain)<\/code> \u4f1a\u4e00\u5c42\u5c42\u5f80\u5916\u627e\uff1ainner \u2192 rainman \u2192 \u5168\u5c40\u3002 \u5185\u5c42\u6ca1\u5b9a\u4e49\u5c31\u7ee7\u7eed\u5411\u5916\uff0c\u76f4\u5230\u5168\u5c40\u5bf9\u8c61\u4e0a\u7684 rain = 1<\/code>\uff0c\u6700\u7ec8\u5f39\u51fa 1\u3002<\/p>\n

<script type=\"text\/javascript\">\n    var rain = 1;\n    function rainman(){\n        var man = 2;\n        function inner(){\n            var innerVar = 4;\n            alert(rain);\n        }\n        inner();    \/\/\u8c03\u7528inner\u51fd\u6570\n    }\n    rainman();    \/\/\u8c03\u7528rainman\u51fd\u6570\n<\/script><\/code><\/pre>\n
\u8fd9\u6761\u94fe\u4e0a\u6709\u4e09\u4e2a\u5bf9\u8c61\uff0c\u987a\u5e8f\u662f inner\u3001rainman\u3001window\u3002\u5f15\u64ce\u8981\u7684\u662f\u53d8\u91cf x \u65f6\uff0c\u4ece\u94fe\u5934\u7b2c\u4e00\u4e2a\u5bf9\u8c61\u627e\u8d77\uff0c\u6ca1\u6709\u518d\u627e\u4e0b\u4e00\u4e2a\u3002<\/p>\n
\u4e8c\u3001\u5c40\u90e8\u53d8\u91cf\u76d6\u4f4f\u540c\u540d\u5168\u5c40\u53d8\u91cf<\/h2>\n
\u51fd\u6570\u4f53\u5185\u540c\u540d\u5c40\u90e8\u53d8\u91cf\u4f18\u5148\u7ea7\u66f4\u9ad8\u3002\u4e0b\u9762 check<\/code> \u91cc\u5f39\u51fa 100\uff0c\u5916\u9762\u4ecd\u662f 1\uff1a<\/p>\n
<script type=\"text\/javascript\">\n    var rain = 1;    \/\/\u5b9a\u4e49\u5168\u5c40\u53d8\u91cf rain\n    function check(){\n        var rain = 100;    \/\/\u5b9a\u4e49\u5c40\u90e8\u53d8\u91cfrain\n        alert( rain );       \/\/\u8fd9\u91cc\u4f1a\u5f39\u51fa 100\n    }\n    check();\n    alert( rain );    \/\/\u8fd9\u91cc\u4f1a\u5f39\u51fa1\n<\/script><\/code><\/pre>\n
\u4e09\u3001var \u6ca1\u6709\u5757\u7ea7\u4f5c\u7528\u57df<\/h2>\n
\u8fd9\u662f\u76f8\u5bf9 C \u7cfb\u8bed\u8a00\u66f4\u300c\u677e\u300d\u7684\u5730\u65b9\u3002if<\/code> \/ for<\/code> \u91cc\u7528 var<\/code> \u58f0\u660e\u7684 i<\/code>\u3001j<\/code>\u3001k<\/code>\uff0c\u4f5c\u7528\u57df\u4ecd\u662f\u6574\u4e2a rainman<\/code> \u51fd\u6570\uff1a<\/p>\n
<script type=\"text\/javascript\">\n    function rainman(){\n        \/\/ rainman\u51fd\u6570\u4f53\u5185\u5b58\u5728\u4e09\u4e2a\u5c40\u90e8\u53d8\u91cf i j k\n        var i = 0;\n        if ( 1 ) {\n            var j = 0;\n            for(var k = 0; k < 3; k++) {\n                alert( k );    \/\/\u5206\u522b\u5f39\u51fa 0 1 2\n            }\n            alert( k );        \/\/\u5f39\u51fa3\n        }\n        alert( j );            \/\/\u5f39\u51fa0\n    }\n<\/script><\/code><\/pre>\n
\u5faa\u73af\u7ed3\u675f\u540e k<\/code> \u662f 3\uff0cif<\/code> \u5916\u9762\u4e5f\u80fd\u8bfb\u5230 j<\/code>\u3002\u82e5\u6539\u6210 let k<\/code>\uff0c\u5faa\u73af\u5916\u518d\u8bfb k<\/code> \u4f1a ReferenceError\u3002<\/p>\n
\u56db\u3001\u51fd\u6570\u5185\u58f0\u660e\u7684\u53d8\u91cf\u6574\u51fd\u6570\u53ef\u89c1<\/h2>\n
\u5185\u5c42 man<\/code> \u6539\u7684\u662f\u5916\u5c42 rain<\/code> \u91cc\u7684 x<\/code>\uff0c\u6240\u4ee5\u5f39\u51fa 100\uff1a<\/p>\n
<script type=\"text\/javascript\">\n    function rain(){\n        var x = 1;\n        function man(){\n            x = 100;\n        }\n        man();        \/\/\u8c03\u7528man\n        alert( x );    \/\/\u8fd9\u91cc\u4f1a\u5f39\u51fa 100\n    }\n    rain();    \/\/\u8c03\u7528rain\n<\/script><\/code><\/pre>\n
\u540c\u4e00\u89c4\u5219\u4f1a\u9020\u6210\u300c\u5148\u8bfb\u540e\u58f0\u660e\u300d\u7684\u9519\u89c9\uff1a<\/p>\n
<script type=\"text\/javascript\">\n    var x = 1;\n    function rain(){\n        alert( x );        \/\/\u5f39\u51fa 'undefined'\uff0c\u800c\u4e0d\u662f1\n        var x = 'rain-man';\n        alert( x );        \/\/\u5f39\u51fa 'rain-man'\n    }\n    rain();\n<\/script><\/code><\/pre>\n
\u56e0\u4e3a var x<\/code> \u5728\u6574\u4e2a rain<\/code> \u91cc\u90fd\u6709\u6548\uff0c\u540c\u540d\u5168\u5c40 x \u88ab\u6321\u4f4f\u3002 \u7b2c\u4e00\u6b21 alert(x)<\/code> \u65f6\u5c40\u90e8 x \u53ea\u5b8c\u6210\u4e86\u58f0\u660e\u3001\u5c1a\u672a\u8d4b\u503c\uff0c\u6240\u4ee5\u662f undefined<\/code>\u3002\u7b49\u4ef7\u4e8e\uff1a<\/p>\n
function rain(){\n    var x;\n    alert( x );\n    x = 'rain-man';\n    alert( x );\n}<\/code><\/pre>\n
\u4e94\u3001\u4e0d\u7528 var \u5c31\u662f\u5168\u5c40\u53d8\u91cf<\/h2>\n
\u8d4b\u503c\u7ed9\u4e00\u4e2a\u4ece\u672a\u58f0\u660e\u7684\u6807\u8bc6\u7b26\uff0c\u4f1a\u5728\u5168\u5c40\u5bf9\u8c61\u4e0a\u521b\u5efa\u5c5e\u6027\u3002\u65b0\u624b\u5e38\u8fd9\u6837\u7559\u4e0b\u4e00\u5806\u5168\u5c40\u53d8\u91cf\uff1a<\/p>\n
<script type=\"text\/javascript\">\n    function rain(){\n        x = 100;    \/\/\u58f0\u660e\u4e86\u5168\u5c40\u53d8\u91cfx\u5e76\u8fdb\u884c\u8d4b\u503c\n    }\n    rain();\n    alert( x );    \/\/\u4f1a\u5f39\u51fa100\n<\/script><\/code><\/pre>\n
\u4e25\u683c\u6a21\u5f0f\uff08'use strict'<\/code>\uff09\u4e0b\u8fd9\u884c\u4f1a\u62a5 ReferenceError<\/code>\uff0c\u5efa\u8bae\u517b\u6210\u59cb\u7ec8\u58f0\u660e\u7684\u4e60\u60ef\u3002<\/p>\n
\u516d\u3001\u5168\u5c40\u53d8\u91cf\u662f window \u7684\u5c5e\u6027<\/h2>\n
\u6d4f\u89c8\u5668\u91cc\u7528 var<\/code> \u58f0\u660e\u7684\u5168\u5c40\uff0c\u7b49\u4ef7\u4e8e\u7ed9 window<\/code> \u6dfb\u5c5e\u6027\uff1a<\/p>\n
<script type=\"text\/javascript\">\n    var x = 100 ;\n    alert( window.x );\/\/\u5f39\u51fa100\n    alert(x);\n<\/script><\/code><\/pre>\n
\u7b49\u540c\u4e8e\uff1a<\/p>\n
<script type=\"text\/javascript\">\n    window.x = 100;\n    alert( window.x );\n    alert(x)\n<\/script><\/code><\/pre>\n\n\n\n\n\n\n\n\n\n
\u89c4\u5219<\/th>\n\u542b\u4e49<\/th>\n\u4f8b\u5b50\u91cc\u7684\u7ed3\u679c<\/th>\n<\/tr>\n<\/thead>\n
\u4f5c\u7528\u57df\u94fe<\/td>\n\u7531\u5185\u5411\u5916\u627e\u6807\u8bc6\u7b26<\/td>\ninner \u80fd\u8bfb\u5230\u5168\u5c40 rain=1<\/td>\n<\/tr>\n
\u540c\u540d\u906e\u853d<\/td>\n\u5c40\u90e8\u4f18\u5148\u4e8e\u5168\u5c40<\/td>\n\u51fd\u6570\u5185 100\uff0c\u51fd\u6570\u5916 1<\/td>\n<\/tr>\n
\u65e0\u5757\u7ea7\uff08var\uff09<\/td>\nif\/for \u91cc\u7684 var \u4ecd\u5c5e\u6574\u4e2a\u51fd\u6570<\/td>\n\u5faa\u73af\u5916\u4ecd\u80fd\u8bfb\u5230 k\u3001j<\/td>\n<\/tr>\n
\u58f0\u660e\u63d0\u5347<\/td>\n\u6574\u4e2a\u51fd\u6570\u90fd\u80fd\u770b\u5230\u8be5\u7ed1\u5b9a<\/td>\n\u8d4b\u503c\u524d\u8bfb\u53d6\u5f97\u5230 undefined<\/td>\n<\/tr>\n
\u6f0f\u5199 var<\/td>\n\u9690\u5f0f\u5168\u5c40<\/td>\n\u51fd\u6570\u5916\u4e5f\u80fd alert(x)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\n
\u4e00\u53e5\u8bdd\u603b\u7ed3\uff1a\u7528 var \u65f6\u53d8\u91cf\u53ea\u8ba4\u51fd\u6570\u4f5c\u7528\u57df\uff1a\u6cbf\u4f5c\u7528\u57df\u94fe\u67e5\u627e\uff0c\u5c40\u90e8\u76d6\u5168\u5c40\uff0c\u5757\u6321\u4e0d\u4f4f\uff0c\u6f0f\u5199 var \u5c31\u4f1a\u6f0f\u5230 window \u4e0a\u3002<\/strong><\/p>\n<\/blockquote>\n<\/section>\n","protected":false},"excerpt":{"rendered":"
\u8c08 JavaScript \u5168\u5c40\u53d8\u91cf\u548c\u5c40\u90e8\u53d8\u91cf\u4e4b\u524d\uff0c\u5148\u8bb0\u4f4f\u4e09\u4ef6\u4e8b\uff1a\u67e5\u627e\u53d8\u91cf\u8d70\u7684\u662f\u4f5c\u7528\u57df\u94fe\uff1b\u7528 var \u65f6\u6ca1\u6709\u5757\u7ea7 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[109],"tags":[150],"_links":{"self":[{"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/posts\/3248"}],"collection":[{"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=3248"}],"version-history":[{"count":1,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/posts\/3248\/revisions"}],"predecessor-version":[{"id":3249,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/posts\/3248\/revisions\/3249"}],"wp:attachment":[{"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3248"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3248"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3248"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}