{"id":1391,"date":"2024-06-02T22:33:41","date_gmt":"2024-06-02T22:33:41","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%e8%af%8d%e6%b3%95%e4%bd%9c%e7%94%a8%e5%9f%9f%e5%92%8c%e5%8a%a8%e6%80%81%e4%bd%9c%e7%94%a8%e5%9f%9f","status":"publish","type":"post","link":"https:\/\/www.lccc.top\/?p=1391","title":{"rendered":"JavaScript\u6df1\u5165\u4e4b\u8bcd\u6cd5\u4f5c\u7528\u57df\u548c\u52a8\u6001\u4f5c\u7528\u57df"},"content":{"rendered":"\n

\u4f5c\u7528\u57df<\/h2>\n

\u4f5c\u7528\u57df\u662f\u6307\u7a0b\u5e8f\u6e90\u4ee3\u7801\u4e2d\u5b9a\u4e49\u53d8\u91cf\u7684\u533a\u57df\u3002<\/p>\n

\u4f5c\u7528\u57df\u89c4\u5b9a\u4e86\u5982\u4f55\u67e5\u627e\u53d8\u91cf\uff0c\u4e5f\u5c31\u662f\u786e\u5b9a\u5f53\u524d\u6267\u884c\u4ee3\u7801\u5bf9\u53d8\u91cf\u7684\u8bbf\u95ee\u6743\u9650\u3002<\/p>\n

JavaScript \u91c7\u7528\u8bcd\u6cd5\u4f5c\u7528\u57df(lexical scoping)\uff0c\u4e5f\u5c31\u662f\u9759\u6001\u4f5c\u7528\u57df\u3002<\/p>\n

\u9759\u6001\u4f5c\u7528\u57df\u4e0e\u52a8\u6001\u4f5c\u7528\u57df<\/h2>\n

\u56e0\u4e3a JavaScript \u91c7\u7528\u7684\u662f\u8bcd\u6cd5\u4f5c\u7528\u57df\uff0c\u51fd\u6570\u7684\u4f5c\u7528\u57df\u5728\u51fd\u6570\u5b9a\u4e49\u7684\u65f6\u5019\u5c31\u51b3\u5b9a\u4e86\u3002<\/p>\n

\u800c\u4e0e\u8bcd\u6cd5\u4f5c\u7528\u57df\u76f8\u5bf9\u7684\u662f\u52a8\u6001\u4f5c\u7528\u57df\uff0c\u51fd\u6570\u7684\u4f5c\u7528\u57df\u662f\u5728\u51fd\u6570\u8c03\u7528\u7684\u65f6\u5019\u624d\u51b3\u5b9a\u7684\u3002<\/p>\n

\u8ba9\u6211\u4eec\u8ba4\u771f\u770b\u4e2a\u4f8b\u5b50\u5c31\u80fd\u660e\u767d\u4e4b\u95f4\u7684\u533a\u522b\uff1a<\/p>\n

<\/p>\n
var<\/span> value<\/span> =<\/span> 1<\/span>;<\/span>\n\nfunction<\/span> foo<\/span>(<\/span>)<\/span> {<\/span>\n    console<\/span>.<\/span>log<\/span>(<\/span>value<\/span>)<\/span>;<\/span>\n}<\/span>\n\nfunction<\/span> bar<\/span>(<\/span>)<\/span> {<\/span>\n    var<\/span> value<\/span> =<\/span> 2<\/span>;<\/span>\n    foo<\/span>(<\/span>)<\/span>;<\/span>\n}<\/span>\n\nbar<\/span>(<\/span>)<\/span>;<\/span>\n\n\/\/ \u7ed3\u679c\u662f ???<\/span><\/pre>\n<\/div>\n
\u5047\u8bbeJavaScript\u91c7\u7528\u9759\u6001\u4f5c\u7528\u57df\uff0c\u8ba9\u6211\u4eec\u5206\u6790\u4e0b\u6267\u884c\u8fc7\u7a0b\uff1a<\/p>\n
\u6267\u884c foo \u51fd\u6570\uff0c\u5148\u4ece foo \u51fd\u6570\u5185\u90e8\u67e5\u627e\u662f\u5426\u6709\u5c40\u90e8\u53d8\u91cf value\uff0c\u5982\u679c\u6ca1\u6709\uff0c\u5c31\u6839\u636e\u4e66\u5199\u7684\u4f4d\u7f6e\uff0c\u67e5\u627e\u4e0a\u9762\u4e00\u5c42\u7684\u4ee3\u7801\uff0c\u4e5f\u5c31\u662f value \u7b49\u4e8e 1\uff0c\u6240\u4ee5\u7ed3\u679c\u4f1a\u6253\u5370 1\u3002<\/p>\n
\u5047\u8bbeJavaScript\u91c7\u7528\u52a8\u6001\u4f5c\u7528\u57df\uff0c\u8ba9\u6211\u4eec\u5206\u6790\u4e0b\u6267\u884c\u8fc7\u7a0b\uff1a<\/p>\n
\u6267\u884c foo \u51fd\u6570\uff0c\u4f9d\u7136\u662f\u4ece foo \u51fd\u6570\u5185\u90e8\u67e5\u627e\u662f\u5426\u6709\u5c40\u90e8\u53d8\u91cf value\u3002\u5982\u679c\u6ca1\u6709\uff0c\u5c31\u4ece\u8c03\u7528\u51fd\u6570\u7684\u4f5c\u7528\u57df\uff0c\u4e5f\u5c31\u662f bar \u51fd\u6570\u5185\u90e8\u67e5\u627e value \u53d8\u91cf\uff0c\u6240\u4ee5\u7ed3\u679c\u4f1a\u6253\u5370 2\u3002<\/p>\n
\u524d\u9762\u6211\u4eec\u5df2\u7ecf\u8bf4\u4e86\uff0cJavaScript\u91c7\u7528\u7684\u662f\u9759\u6001\u4f5c\u7528\u57df\uff0c\u6240\u4ee5\u8fd9\u4e2a\u4f8b\u5b50\u7684\u7ed3\u679c\u662f 1\u3002<\/p>\n
\u52a8\u6001\u4f5c\u7528\u57df<\/h2>\n
\u4e5f\u8bb8\u4f60\u4f1a\u597d\u5947\u4ec0\u4e48\u8bed\u8a00\u662f\u52a8\u6001\u4f5c\u7528\u57df\uff1f<\/p>\n
bash \u5c31\u662f\u52a8\u6001\u4f5c\u7528\u57df\uff0c\u4e0d\u4fe1\u7684\u8bdd\uff0c\u628a\u4e0b\u9762\u7684\u811a\u672c\u5b58\u6210\u4f8b\u5982 scope.bash\uff0c\u7136\u540e\u8fdb\u5165\u76f8\u5e94\u7684\u76ee\u5f55\uff0c\u7528\u547d\u4ee4\u884c\u6267\u884c bash .\/scope.bash<\/code>\uff0c\u770b\u770b\u6253\u5370\u7684\u503c\u662f\u591a\u5c11\u3002<\/p>\n
<\/p>\n
value=1\nfunction<\/span> foo<\/span> () {\n    echo<\/span> $value<\/span>;<\/span>\n}\nfunction<\/span> bar<\/span> () {\n    local<\/span> value=2;<\/span>\n    foo;<\/span>\n}\nbar<\/pre>\n<\/div>\n
\u8fd9\u4e2a\u6587\u4ef6\u4e5f\u53ef\u4ee5\u5728 Github \u535a\u5ba2\u4ed3\u5e93<\/a>\u4e2d\u627e\u5230\u3002<\/p>\n
\u601d\u8003\u9898<\/h2>\n
\u6700\u540e\uff0c\u8ba9\u6211\u4eec\u770b\u4e00\u4e2a\u300aJavaScript\u6743\u5a01\u6307\u5357\u300b\u4e2d\u7684\u4f8b\u5b50\uff1a<\/p>\n
<\/p>\n
var<\/span> scope<\/span> =<\/span> \"global scope\"<\/span>;<\/span>\nfunction<\/span> checkscope<\/span>(<\/span>)<\/span>{<\/span>\n    var<\/span> scope<\/span> =<\/span> \"local scope\"<\/span>;<\/span>\n    function<\/span> f<\/span>(<\/span>)<\/span>{<\/span>\n        return<\/span> scope<\/span>;<\/span>\n    }<\/span>\n    return<\/span> f<\/span>(<\/span>)<\/span>;<\/span>\n}<\/span>\ncheckscope<\/span>(<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
<\/p>\n
var<\/span> scope<\/span> =<\/span> \"global scope\"<\/span>;<\/span>\nfunction<\/span> checkscope<\/span>(<\/span>)<\/span>{<\/span>\n    var<\/span> scope<\/span> =<\/span> \"local scope\"<\/span>;<\/span>\n    function<\/span> f<\/span>(<\/span>)<\/span>{<\/span>\n        return<\/span> scope<\/span>;<\/span>\n    }<\/span>\n    return<\/span> f<\/span>;<\/span>\n}<\/span>\ncheckscope<\/span>(<\/span>)<\/span>(<\/span>)<\/span>;<\/span><\/pre>\n<\/div>\n
\u731c\u731c\u4e24\u6bb5\u4ee3\u7801\u5404\u81ea\u7684\u6267\u884c\u7ed3\u679c\u662f\u591a\u5c11\uff1f<\/p>\n
\u8fd9\u91cc\u76f4\u63a5\u544a\u8bc9\u5927\u5bb6\u7ed3\u679c\uff0c\u4e24\u6bb5\u4ee3\u7801\u90fd\u4f1a\u6253\u5370\uff1alocal scope<\/code>\u3002<\/p>\n
\u539f\u56e0\u4e5f\u5f88\u7b80\u5355\uff0c\u56e0\u4e3aJavaScript\u91c7\u7528\u7684\u662f\u8bcd\u6cd5\u4f5c\u7528\u57df\uff0c\u51fd\u6570\u7684\u4f5c\u7528\u57df\u57fa\u4e8e\u51fd\u6570\u521b\u5efa\u7684\u4f4d\u7f6e\u3002<\/p>\n
\u800c\u5f15\u7528\u300aJavaScript\u6743\u5a01\u6307\u5357\u300b\u7684\u56de\u7b54\u5c31\u662f\uff1a<\/p>\n
JavaScript \u51fd\u6570\u7684\u6267\u884c\u7528\u5230\u4e86\u4f5c\u7528\u57df\u94fe\uff0c\u8fd9\u4e2a\u4f5c\u7528\u57df\u94fe\u662f\u5728\u51fd\u6570\u5b9a\u4e49\u7684\u65f6\u5019\u521b\u5efa\u7684\u3002\u5d4c\u5957\u7684\u51fd\u6570 f() \u5b9a\u4e49\u5728\u8fd9\u4e2a\u4f5c\u7528\u57df\u94fe\u91cc\uff0c\u5176\u4e2d\u7684\u53d8\u91cf scope \u4e00\u5b9a\u662f\u5c40\u90e8\u53d8\u91cf\uff0c\u4e0d\u7ba1\u4f55\u65f6\u4f55\u5730\u6267\u884c\u51fd\u6570 f()\uff0c\u8fd9\u79cd\u7ed1\u5b9a\u5728\u6267\u884c f() \u65f6\u4f9d\u7136\u6709\u6548\u3002<\/p>\n
\u4f46\u662f\u5728\u8fd9\u91cc\u771f\u6b63\u60f3\u8ba9\u5927\u5bb6\u601d\u8003\u7684\u662f\uff1a<\/p>\n
\u867d\u7136\u4e24\u6bb5\u4ee3\u7801\u6267\u884c\u7684\u7ed3\u679c\u4e00\u6837\uff0c\u4f46\u662f\u4e24\u6bb5\u4ee3\u7801\u7a76\u7adf\u6709\u54ea\u4e9b\u4e0d\u540c\u5462\uff1f<\/p>\n
\u5982\u679c\u8981\u56de\u7b54\u8fd9\u4e2a\u95ee\u9898\uff0c\u5c31\u8981\u7275\u6d89\u5230\u5f88\u591a\u7684\u5185\u5bb9\uff0c\u8bcd\u6cd5\u4f5c\u7528\u57df\u53ea\u662f\u5176\u4e2d\u7684\u4e00\u5c0f\u90e8\u5206\uff0c\u8ba9\u6211\u4eec\u671f\u5f85\u4e0b\u4e00\u7bc7\u6587\u7ae0\u2014\u2014\u2014\u2014\u300aJavaScript\u6df1\u5165\u4e4b\u6267\u884c\u4e0a\u4e0b\u6587\u6808\u300b\u3002<\/p>\n
\u4e0b\u4e00\u7bc7\u6587\u7ae0<\/h2>\n
JavaScript\u6df1\u5165\u4e4b\u6267\u884c\u4e0a\u4e0b\u6587\u6808<\/a><\/p>\n
\u6df1\u5165\u7cfb\u5217<\/h2>\n
JavaScript\u6df1\u5165\u7cfb\u5217\u76ee\u5f55\u5730\u5740\uff1ahttps:\/\/github.com\/mqyqingfeng\/Blog<\/a>\u3002<\/p>\n
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
\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
\u6587\u7ae0\u8f6c\u8f7d\u81eahttps:\/\/github.com\/mqyqingfeng\/Blog\/issues\/3<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
\u4f5c\u7528\u57df \u4f5c\u7528\u57df\u662f\u6307\u7a0b\u5e8f\u6e90\u4ee3\u7801\u4e2d\u5b9a\u4e49\u53d8\u91cf\u7684\u533a\u57df\u3002 \u4f5c\u7528\u57df\u89c4\u5b9a\u4e86\u5982\u4f55\u67e5\u627e\u53d8\u91cf\uff0c\u4e5f\u5c31\u662f\u786e\u5b9a\u5f53\u524d\u6267\u884c\u4ee3\u7801\u5bf9\u53d8\u91cf\u7684\u8bbf\u95ee\u6743\u9650\u3002 JavaScript \u91c7\u7528\u8bcd\u6cd5\u4f5c\u7528\u57df(lex…<\/p>\n
 Read More  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-1391","post","type-post","status-publish","format-standard","hentry","category-learn"],"_links":{"self":[{"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts\/1391"}],"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=1391"}],"version-history":[{"count":1,"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts\/1391\/revisions"}],"predecessor-version":[{"id":1490,"href":"https:\/\/www.lccc.top\/index.php?rest_route=\/wp\/v2\/posts\/1391\/revisions\/1490"}],"wp:attachment":[{"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1391"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1391"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lccc.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1391"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}