{"id":2154,"date":"2018-04-09T09:18:00","date_gmt":"2018-04-09T01:18:00","guid":{"rendered":"http:\/\/www.imzouyang.com\/blog\/?p=2154"},"modified":"2020-10-28T22:46:47","modified_gmt":"2020-10-28T14:46:47","slug":"js%e5%8e%9f%e7%90%86%ef%bc%9a%e9%97%ad%e5%8c%85","status":"publish","type":"post","link":"http:\/\/www.imzouyang.com\/blog\/archives\/2154.html","title":{"rendered":"js\u539f\u7406\uff1a\u95ed\u5305"},"content":{"rendered":"\n<p><strong>\u4e00\u3001\u4ec0\u4e48\u662f\u95ed\u5305\uff1a<\/strong><\/p>\n\n\n\n<p>\u4e00\u53e5\u8bdd\uff1a<strong>\u5b50\u51fd\u6570<\/strong>\u4f7f\u7528<strong>\u7236\u51fd\u6570<\/strong>\u7684<strong>\u5c40\u90e8\u53d8\u91cf<\/strong> \u7684\u60c5\u5f62\uff0c\u5c31\u662f\u95ed\u5305\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/\u60f3\u8ba9\u51fd\u6570\u5185\u7684\u5c40\u90e8\u53d8\u91cf\u5b9e\u73b0\u7d2f\u52a0\n\/\/\u793a\u4f8b1\uff0c\u4e0d\u4f7f\u7528\u95ed\u5305\uff0c\u6ca1\u6cd5\u5b9e\u73b0\u7d2f\u52a0\nfunction Foo(){\n     var i=0;\n     return ++i;\n}\nvar f1=Foo;\nconsole.log(f1());  \/\/1\nconsole.log(f1());  \/\/1\nconsole.log(f1());  \/\/1\n\n\n\/\/\u4f7f\u7528\u95ed\u5305\uff0c\u5b50\u51fd\u6570\u8bbf\u95ee\u7236\u51fd\u6570\u5185\u7684\u5c40\u90e8\u53d8\u91cf\nfunction Foo(){  \/\/\u7236\u51fd\u6570\n     var i=0;\n     return function(){  \/\/\u5b50\u51fd\u6570\n         console.log(++i);  \/\/\u5b50\u51fd\u6570\u4f7f\u7528\u4e86\u7236\u51fd\u6570\u7684\u5c40\u90e8\u53d8\u91cf i\n     }\n}\nvar f1=Foo(); \/\/Foo\u51fd\u6570\u867d\u7136return\u4e86\uff0c\u6267\u884c\u5b8c\u4e86\uff1b\u4f46\u662f\u5c40\u90e8\u53d8\u91cf i \u5e76\u6ca1\u6709\u88ab\u9500\u6bc1\nf1(); \/\/1        \/\/\u5c40\u90e8\u53d8\u91cfi\u5728\u88ab\u7d2f\u52a0\nf1(); \/\/2\nf1(); \/\/3\n<\/code><\/pre>\n\n\n\n<p><strong>\u4e8c\u3001\u95ed\u5305\u7684\u4f5c\u7528\uff1a<\/strong><\/p>\n\n\n\n<p>\u5b50\u51fd\u6570\u4f7f\u7528\u7684\u7236\u51fd\u6570\u7684\u5c40\u90e8\u53d8\u91cf\u4f1a\u88ab\u9a7b\u7559\u5728\u5185\u5b58\u4e2d\u800c\u4e0d\u4f1a\u88ab\u5783\u573e\u56de\u6536\u673a\u5236\u9500\u6bc1\u3002<\/p>\n\n\n\n<p><strong>\u4e09\u3001\u4e3a\u4f55\u9700\u8981\u95ed\u5305\uff1a<\/strong><\/p>\n\n\n\n<p>\u5f53\u6211\u4eec\u60f3\u8981\u7ee7\u7eed\u4f7f\u7528 \u51fd\u6570\u5185 \u5c40\u90e8\u53d8\u91cf\u65f6\uff0c\u5c31\u9700\u8981\u95ed\u5305\u3002<br><br>\u51fd\u6570\u4ee3\u7801\u7684\u6267\u884c\u9700\u8981\u5360\u7528\u5185\u5b58\uff0c\u4e00\u4e2a\u51fd\u6570\u6267\u884c\u5185\u90e8\u53ea\u6267\u884c\u4e00\u6b21\uff0c\u6267\u884c\u5b8c\u4e86\u8fd4\u56de\uff0c\u5e76\u4ece\u5185\u5b58\u4e2d\u6e05\u9664\u8be5\u51fd\u6570\u5185\u7533\u660e\u7684\u4e00\u5207\u6570\u636e(\u53d8\u91cf)\uff0c\u4ee5\u91ca\u653e\u5185\u5b58\u3002\uff08\u51fd\u6570\u4e00\u5b9a\u4f1a\u8fd4\u56de\uff0c\u8981\u561b\u65e0\u8fd4\u56de\u503c\u7684\u8fd4\u56deundefined\uff0c\u8981\u561b\u8fd4\u56de\u5176\u5b83\u7684\uff0c\u800c\u8fd4\u56de\u540e\u8be5\u51fd\u6570\u6267\u884c\u65f6\u7684\u90a3\u4e9b\u4e0a\u4e0b\u6587\u4f1a\u88ab\u5783\u573e\u56de\u6536\u3002\uff09<br>\u8d1f\u8d23\u91ca\u653e\u5185\u5b58\u7684\u673a\u5236\u662f js\u7684\u5783\u573e\u56de\u6536\u673a\u5236\u3002\u5f53\u6211\u4eec\u60f3\u8981\u51fd\u6570\u5185\u7684\u53d8\u91cf\u4e0d\u88ab\u5783\u573e\u56de\u6536\u3002\u5c31\u9700\u8981\u4f7f\u7528\u95ed\u5305\u3002\u5f53\u5783\u573e\u56de\u6536\u673a\u5236\u8981\u56de\u6536\u5c40\u90e8\u53d8\u91cf\u65f6\uff0c\u53d1\u73b0\u8be5\u53d8\u91cf\u8fd8\u88ab\u5b50\u51fd\u6570\u7ee7\u7eed\u4f7f\u7528\u7740\uff0c\u4ece\u800c\u4e0d\u4f1a\u56de\u6536\u5b83\u3002\uff08\u5982\u679c\u56de\u6536\u4e86\u5b83\uff0c\u5b50\u51fd\u6570\u5c31\u6ca1\u6cd5\u6b63\u786e\u6267\u884c\u4e86\uff09<\/p>\n\n\n\n<p><strong>\u56db\u3001\u95ed\u5305\u5b9e\u73b0\u9700\u6ce8\u610f\uff1a<\/strong><\/p>\n\n\n\n<ul><li>1\u3001\u51fd\u6570\u9700\u8981return\u51fa\u53bb &nbsp; <\/li><li>2\u3001return\u51fa\u53bb\u7684\u503c\u662f\u4e00\u4e2a\u5f15\u7528\u7c7b\u578b &nbsp;<\/li><li>3\u3001\u4f7f\u7528return\u51fa\u53bb\u7684\u51fd\u6570\u65f6\u624d\u4f1a\u6709\u9a7b\u7559\u5185\u5b58\u6548\u679c\uff0c\u5149\u662f\u4f7f\u7528\u51fd\u6570fn1\u662f\u6ca1\u6709\u95ed\u5305\u6548\u679c\u7684 &nbsp; <\/li><li>4\u3001return \u7684\u90a3\u4e2a\u51fd\u6570\u5c31\u662f\u95ed\u5305\u4e86\uff0c\u91cc\u9762\u7684this\u662f\u6307\u5411window\u7684\uff0creturn\u51fa\u53bb\u7684\u90a3\u4e2a\u51fd\u6570\u91cc\u9762\u4f7f\u7528\u7684\u53d8\u91cf\u662f\u7236\u51fd\u6570\u7684\u5c40\u90e8\u53d8\u91cf\uff0c\u5982\u679c\u8981\u7528\u5168\u5c40\u7684\u53d8\u91cf\uff0c\u53ef\u4ee5\u52a0\u4e0athis\u5c31\u53ef\u4ee5:<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/\u4f7f\u7528\u5168\u5c40\u53d8\u91cf\nvar a = 9;\nfunction fn1() {\n    var a = 1;\n    return function () {\n        console.log(this.a);\n        console.log(this.a++);\n    }\n}\nfn1()();    \/\/9 9   \u53bb\u6389a\u524d\u9762\u7684this\uff0c\u5c31\u4f1a\u6253\u53701 1\nfn1()();    \/\/10 10   \u53bb\u6389a\u524d\u9762\u7684this\uff0c\u5c31\u4f1a\u6253\u53701 1\nfn1()();    \/\/11 11   \u53bb\u6389a\u524d\u9762\u7684this\uff0c\u5c31\u4f1a\u6253\u53701 1<\/code><\/pre>\n\n\n\n<p><strong>\u4e94\u3001\u95ed\u5305\u4f18\u7f3a\u70b9\uff1a<\/strong><\/p>\n\n\n\n<p>\u5b83\u7684\u4f18\u70b9\u65e2\u662f\u4ed6\u7684\u7f3a\u70b9\uff0c<br>\u4f18\u70b9\uff1a\u5c40\u90e8\u53d8\u91cf\u9a7b\u7559\u5185\u5b58\uff0c\u4ece\u800c\u907f\u514d\u4f7f\u7528\u5168\u5c40\u53d8\u91cf\uff0c\u907f\u514d\u4e86\u5168\u5c40\u53d8\u91cf\u7684\u6c61\u67d3\u95ee\u9898\u3002<br>\u7f3a\u70b9\uff1a\u56e0\u4e3a\u95ed\u5305\u5c06\u5c40\u90e8\u53d8\u91cf\u9a7b\u7559\u5185\u5b58\u4e86\uff0c\u6240\u4ee5\u4f7f\u7528\u4e0d\u5f53\uff0c\u5bb9\u6613\u9020\u6210 \u5185\u5b58\u6cc4\u6f0f\u3002<br><br><br>\u5176\u5b9e\uff0c\u66f4\u786e\u5207\u7684\u8bf4\uff0c\u95ed\u5305\u8ddf\u5185\u5b58\u6cc4\u6f0f\u5e76\u4e0d\u662f\u76f4\u63a5\u56e0\u679c\u5173\u7cfb\uff0c\u6211\u4eec\u9009\u62e9\u628a\u8981\u4f7f\u7528\u7684\u53d8\u91cf\u653e\u5728\u95ed\u5305\u4e2d\uff0c\u548c\u653e\u5728\u5168\u5c40\u4e2d\uff0c\u5bf9\u5185\u5b58\u7684\u5f71\u54cd\u662f\u4e00\u81f4\u7684\u3002\u4ece\u8fd9\u770b\u5e76\u4e0d\u80fd\u8bf4\u6210\u662f\u5185\u5b58\u6cc4\u6f0f\u3002\u5982\u679c\u5728\u5c06\u6765\u4e0d\u9700\u8981\u4f7f\u7528\u8fd9\u4e9b\u53d8\u91cf\u65f6\uff0c\u6211\u4eec\u53ef\u4ee5\u624b\u52a8\u5c06\u8fd9\u4e9b\u53d8\u91cf\u8bbe\u7f6enull\u3002\u8ba9\u95ed\u5305\u8ddf\u5185\u5b58\u6cc4\u6f0f\u6709\u5173\u7cfb\u7684\uff0c\u662f\u6211\u4eec\u4f7f\u7528\u7684\u4e0d\u5f53\uff0c\u6bd4\u5982\u6211\u4eec\u4f7f\u7528\u95ed\u5305\u7684\u540c\u65f6\uff0c\u53c8\u6709\u5faa\u73af\u5f15\u7528\uff08\u5728\u5783\u573e\u56de\u6536\u673a\u5236\u4e2d\uff0c\u5982\u679c\u4e24\u4e2a\u5bf9\u8c61\u76f8\u4e92\u4e4b\u95f4\u5f62\u6210\u4e86\u5faa\u73af\u5f15\u7528\uff0c\u90a3\u4e48\u8fd9\u4e24\u4e2a\u5bf9\u8c61\u90fd\u65e0\u6cd5\u88ab\u56de\u6536\uff09\u3002\u5faa\u73af\u5f15\u7528\u9020\u6210\u7684\u5185\u5b58\u6cc4\u6f0f\uff0c\u8fd9\u672c\u8eab\u5e76\u975e\u95ed\u5305\u7684\u95ee\u9898\u3002<\/p>\n\n\n\n<p><strong>\u516d\u3001\u66f4\u591a\u95ed\u5305\u793a\u4f8b\uff1a<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>function fn1() {\n    var a = 1;\n    function fn2() {\n        alert(a);\n        alert(a++);\n    }\n    return fn2; \/\/\u8fd4\u56de\u51fa\u53bb\u7684\u662f\u4e00\u4e2a\u5f15\u7528\u7c7b\u578b\u7684\u503c\n}\nvar f = fn1();\n f();    \/\/\u8fd4\u56de1  \u8fd4\u56de1\n f();    \/\/\u8fd4\u56de2  \u8fd4\u56de2\n f();    \/\/\u8fd4\u56de3  \u8fd4\u56de3\nvar f = 1;\nvar f = fn1();\nf()    \/\/\u8fd4\u56de1  \u8fd4\u56de1\uff0c\u56e0\u4e3a\u4e4b\u524d\u7684f=1\u7684\u8d4b\u503c\u5df2\u7ecf\u65ad\u5f00\u4e86f\u4e0efn1\u7684\u8fde\u63a5\u4e86\uff0c\u7136\u540efn1\u5c31\u88ab\u5783\u573e\u56de\u6536\u4e86\n\n\nfunction Foo() {\n    var i = 0;\n    return function () {\n        console.log(i++);\n    }\n}\nvar f1 = Foo(), f2 = Foo();    \/\/\u7ed9\u53d8\u91cff1  f2\u8d4b\u503c\nf1(); \/\/0\nf1(); \/\/1\nf2(); \/\/0\nf1(); \/\/2\n\/\/\u8fd9\u91ccf1()\u51fd\u6570\u548cf2()\u51fd\u6570\u5728\u8c03\u7528\u65f6\u4f1a\u521b\u5efa\u4e24\u4e2a\u6267\u884c\u73af\u5883\uff0c\u4fdd\u5b58\u5404\u81ea\u7684\u53d8\u91cf\u5bf9\u8c61\n\n\nfunction fn1() {\n    var a = 1;\n    function fn2() {\n        alert(a);\n        alert(a++);\n    }\n    return fn2; \/\/\u8fd4\u56de\u51fa\u53bb\u7684\u662f\u4e00\u4e2a\u5f15\u7528\u7c7b\u578b\u7684\u503c\n}\nvar f = fn1;       \/\/\u6ce8\u610f\u6b64\u65f6fn1\u6ca1\u6709\u62ec\u53f7,\u6240\u4ee5f\u7684\u5f15\u7528\u5730\u5740\u53ea\u662f\u51fd\u6570fn1,\u4e0d\u662f\u5b83\u5185\u90e8\u7684return\u5185\u5bb9\nf()();     \/\/\u8fd4\u56de1  \u8fd4\u56de1\nf()();    \/\/\u8fd4\u56de1  \u8fd4\u56de1\nf()();    \/\/\u8fd4\u56de1  \u8fd4\u56de1<\/code><\/pre>\n\n\n\n<p>\u4e66\u4e0a\u4e00\u4e2a\u793a\u4f8b\uff1a\uff08\u5177\u4f53\u51fa\u81ea\u54ea\u672c\u4e66\uff0c\u5f53\u65f6\u505a\u7b14\u8bb0\u6ca1\u6709\u5907\u6ce8\u4e0a\uff0c\u65e0\u6cd5\u6ce8\u91ca\u5f15\u7528\u4e86\uff0c\u540e\u9762\u77e5\u9053\u4e86\u518d\u8865\u5145\u4e66\u540d\uff09<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" width=\"553\" height=\"700\" src=\"http:\/\/www.imzouyang.com\/blog\/wp-content\/uploads\/2020\/07\/clipboard5.jpg\" alt=\"\" class=\"wp-image-2158\" srcset=\"http:\/\/www.imzouyang.com\/blog\/wp-content\/uploads\/2020\/07\/clipboard5.jpg 553w, http:\/\/www.imzouyang.com\/blog\/wp-content\/uploads\/2020\/07\/clipboard5-237x300.jpg 237w\" sizes=\"(max-width: 553px) 100vw, 553px\" \/><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>\u4e00\u3001\u4ec0\u4e48\u662f\u95ed\u5305\uff1a \u4e00\u53e5\u8bdd\uff1a\u5b50\u51fd\u6570\u4f7f\u7528\u7236\u51fd\u6570\u7684\u5c40\u90e8\u53d8\u91cf \u7684\u60c5\u5f62\uff0c\u5c31\u662f\u95ed\u5305\u3002 \u4e8c\u3001\u95ed\u5305\u7684\u4f5c\u7528\uff1a \u5b50\u51fd\u6570\u4f7f\u7528\u7684\u7236\u51fd\u6570 &hellip; <a href=\"http:\/\/www.imzouyang.com\/blog\/archives\/2154.html\" class=\"read-more\">\u7ee7\u7eed\u9605\u8bfb <span class=\"screen-reader-text sr-only\">js\u539f\u7406\uff1a\u95ed\u5305<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"aside","meta":[],"categories":[30],"tags":[],"_links":{"self":[{"href":"http:\/\/www.imzouyang.com\/blog\/wp-json\/wp\/v2\/posts\/2154"}],"collection":[{"href":"http:\/\/www.imzouyang.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.imzouyang.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.imzouyang.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.imzouyang.com\/blog\/wp-json\/wp\/v2\/comments?post=2154"}],"version-history":[{"count":3,"href":"http:\/\/www.imzouyang.com\/blog\/wp-json\/wp\/v2\/posts\/2154\/revisions"}],"predecessor-version":[{"id":2161,"href":"http:\/\/www.imzouyang.com\/blog\/wp-json\/wp\/v2\/posts\/2154\/revisions\/2161"}],"wp:attachment":[{"href":"http:\/\/www.imzouyang.com\/blog\/wp-json\/wp\/v2\/media?parent=2154"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.imzouyang.com\/blog\/wp-json\/wp\/v2\/categories?post=2154"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.imzouyang.com\/blog\/wp-json\/wp\/v2\/tags?post=2154"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}