{"id":12232,"date":"2023-11-28T22:47:47","date_gmt":"2023-11-28T14:47:47","guid":{"rendered":"https:\/\/wx.kaifamiao.info\/?p=12232"},"modified":"2023-11-29T23:19:12","modified_gmt":"2023-11-29T15:19:12","slug":"javascript-zhong-shen-me-shi-zuo-yong-yu","status":"publish","type":"post","link":"http:\/\/wx.kaifamiao.info\/index.php\/2023\/11\/28\/javascript-zhong-shen-me-shi-zuo-yong-yu\/","title":{"rendered":"JavaScript \u4e2d\u4ec0\u4e48\u662f\u4f5c\u7528\u57df\uff1f"},"content":{"rendered":"

\u5728 JavaScript \u4e2d\uff0c\u4f5c\u7528\u57df\u6307\u7684\u662f\u53d8\u91cf\uff08\u6216\u51fd\u6570\uff09\u7684\u53ef\u8bbf\u95ee\u6027\u548c\u53ef\u89c1\u6027\u7684\u8303\u56f4\u3002\u5b83\u89c4\u5b9a\u4e86\u5728\u4ee3\u7801\u4e2d\u7684\u67d0\u4e2a\u4f4d\u7f6e\uff0c\u53d8\u91cf\u548c\u51fd\u6570\u53ef\u4ee5\u88ab\u5f15\u7528\u7684\u533a\u57df\u3002<\/p>\n

\u4e3b\u8981\u6709\u4e24\u79cd\u4f5c\u7528\u57df\uff1a<\/p>\n

    \n
  1. \n

    \u5168\u5c40\u4f5c\u7528\u57df\uff08Global Scope\uff09<\/strong>\uff1a\u5168\u5c40\u4f5c\u7528\u57df\u662f\u6574\u4e2a\u7a0b\u5e8f\u7684\u6700\u5916\u5c42\u4f5c\u7528\u57df\uff0c\u5b9a\u4e49\u5728\u4efb\u4f55\u51fd\u6570\u3001\u4ee3\u7801\u5757\u6216\u5176\u4ed6\u4f5c\u7528\u57df\u4e4b\u5916\u7684\u53d8\u91cf\u6216\u51fd\u6570\u90fd\u5c5e\u4e8e\u5168\u5c40\u4f5c\u7528\u57df\u3002\u5728\u5168\u5c40\u4f5c\u7528\u57df\u4e2d\u58f0\u660e\u7684\u53d8\u91cf\u548c\u51fd\u6570\u53ef\u4ee5\u88ab\u4ee3\u7801\u4e2d\u7684\u4efb\u4f55\u90e8\u5206\u8bbf\u95ee\u3002<\/p>\n<\/li>\n

  2. \n

    \u5c40\u90e8\u4f5c\u7528\u57df\uff08Local Scope\uff09<\/strong>\uff1a\u5c40\u90e8\u4f5c\u7528\u57df\u662f\u5728\u51fd\u6570\u5185\u90e8\u58f0\u660e\u7684\u4f5c\u7528\u57df\uff0c\u5373\u51fd\u6570\u5185\u90e8\u7684\u53d8\u91cf\u548c\u51fd\u6570\u53ea\u80fd\u5728\u8be5\u51fd\u6570\u5185\u90e8\u8bbf\u95ee\u3002\u6bcf\u6b21\u8c03\u7528\u51fd\u6570\u65f6\uff0c\u90fd\u4f1a\u521b\u5efa\u4e00\u4e2a\u65b0\u7684\u5c40\u90e8\u4f5c\u7528\u57df\u3002<\/p>\n<\/li>\n<\/ol>\n

    JavaScript \u4e2d\u4f5c\u7528\u57df\u7684\u7279\u70b9\uff1a<\/p>\n

      \n
    • \u4f5c\u7528\u57df\u94fe\uff08Scope Chain\uff09<\/strong>\uff1a\u5185\u90e8\u4f5c\u7528\u57df\u53ef\u4ee5\u8bbf\u95ee\u5916\u90e8\u4f5c\u7528\u57df\u4e2d\u7684\u53d8\u91cf\uff0c\u4f46\u53cd\u4e4b\u4e0d\u6210\u7acb\u3002\u8fd9\u79cd\u5d4c\u5957\u7684\u4f5c\u7528\u57df\u5f62\u6210\u4e86\u4f5c\u7528\u57df\u94fe\u3002<\/li>\n
    • \u53d8\u91cf\u63d0\u5347\uff08Hoisting\uff09<\/strong>\uff1aJavaScript \u4e2d\u53d8\u91cf\u548c\u51fd\u6570\u58f0\u660e\u4f1a\u88ab\u63d0\u5347\u5230\u5176\u6240\u5728\u4f5c\u7528\u57df\u7684\u9876\u90e8\uff0c\u4f46\u8d4b\u503c\u4e0d\u4f1a\u63d0\u5347\u3002\u8fd9\u610f\u5473\u7740\u53ef\u4ee5\u5728\u58f0\u660e\u4e4b\u524d\u4f7f\u7528\u53d8\u91cf\uff0c\u4f46\u5b83\u7684\u503c\u4f1a\u662f undefined<\/code>\u3002<\/li>\n
    • \u5757\u7ea7\u4f5c\u7528\u57df<\/strong>\uff1a\u5728 ES6 \u5f15\u5165 let<\/code> \u548c const<\/code> \u540e\uff0c\u53ef\u4ee5\u901a\u8fc7\u5b83\u4eec\u521b\u5efa\u5757\u7ea7\u4f5c\u7528\u57df\uff0c\u5373\u5728 {}<\/code> \u5185\u90e8\u5b9a\u4e49\u7684\u53d8\u91cf\u53ea\u5728\u8be5\u5757\u5185\u6709\u6548\u3002<\/li>\n<\/ul>\n

      \u7406\u89e3\u4f5c\u7528\u57df\u5bf9\u4e8e\u7f16\u5199\u53ef\u7ef4\u62a4\u548c\u53ef\u9884\u6d4b\u7684\u4ee3\u7801\u975e\u5e38\u91cd\u8981\uff0c\u5b83\u5f71\u54cd\u7740\u53d8\u91cf\u7684\u8bbf\u95ee\u3001\u751f\u547d\u5468\u671f\u548c\u53ef\u89c1\u6027\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"

      \u5728 JavaScript \u4e2d\uff0c\u4f5c\u7528\u57df\u6307\u7684\u662f\u53d8\u91cf\uff08\u6216\u51fd\u6570\uff09\u7684\u53ef\u8bbf\u95ee\u6027\u548c\u53ef\u89c1\u6027\u7684\u8303\u56f4\u3002\u5b83\u89c4\u5b9a\u4e86\u5728\u4ee3\u7801\u4e2d\u7684\u67d0\u4e2a\u4f4d\u7f6e\uff0c […]<\/p>\n","protected":false},"author":11,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[115],"tags":[],"class_list":["post-12232","post","type-post","status-publish","format-standard","hentry","category-javascript"],"_links":{"self":[{"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/posts\/12232","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/users\/11"}],"replies":[{"embeddable":true,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/comments?post=12232"}],"version-history":[{"count":2,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/posts\/12232\/revisions"}],"predecessor-version":[{"id":13586,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/posts\/12232\/revisions\/13586"}],"wp:attachment":[{"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/media?parent=12232"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/categories?post=12232"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/tags?post=12232"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}