{"id":15037,"date":"2024-10-11T17:49:37","date_gmt":"2024-10-11T09:49:37","guid":{"rendered":"https:\/\/fgchen.com\/wpedu\/?p=15037"},"modified":"2026-03-30T14:29:17","modified_gmt":"2026-03-30T06:29:17","slug":"javascript-%e7%9a%84%e8%ae%8a%e6%95%b8%e7%bd%ae%e9%a0%82%ef%bc%88variable-hoisting%ef%bc%89","status":"publish","type":"post","link":"https:\/\/fgchen.com\/wpedu\/2024\/10\/javascript-%e7%9a%84%e8%ae%8a%e6%95%b8%e7%bd%ae%e9%a0%82%ef%bc%88variable-hoisting%ef%bc%89\/","title":{"rendered":"JavaScript \u7684\u8b8a\u6578\u7f6e\u9802\uff08Variable Hoisting\uff09"},"content":{"rendered":"

JavaScript \u7684\u8b8a\u6578\u7f6e\u9802\uff08Variable Hoisting\uff09<\/p>\n

\u8b8a\u6578\u7f6e\u9802\u662f JavaScript \u4e2d\u7684\u4e00\u500b\u884c\u70ba\uff0c\u5b83\u6307\u7684\u662f\u8b8a\u6578\u548c\u51fd\u5f0f\u7684\u5ba3\u544a\u6703\u5728\u7de8\u8b6f\u968e\u6bb5\u88ab\u79fb\u5230\u5176\u6240\u5728\u4f5c\u7528\u57df\u7684\u6700\u9802\u90e8\u3002\u9019\u500b\u884c\u70ba\u5c31\u50cf\u9019\u4e9b\u5ba3\u544a\u88ab"\u63d0\u5347"\u6216"\u7f6e\u9802"\u5230\u4e86\u4f5c\u7528\u57df\u7684\u9802\u90e8\uff0c\u56e0\u6b64\u5f97\u540d\u3002<\/p>\n

\u4ee5\u4e0b\u662f\u8b8a\u6578\u7f6e\u9802\u7684\u5e7e\u500b\u91cd\u8981\u7279\u9ede\uff1a<\/p>\n

    \n
  1. var \u7684\u7f6e\u9802\uff1a<\/li>\n<\/ol>\n
    console.log(x); \/\/ \u8f38\u51fa\uff1aundefined\nvar x = 5;\n\n\/\/ \u4e0a\u9762\u7684\u7a0b\u5f0f\u78bc\u7b49\u540c\u65bc\uff1a\nvar x;\nconsole.log(x);\nx = 5;<\/code><\/pre>\n
    var \u5ba3\u544a\u7684\u8b8a\u6578\u6703\u88ab\u7f6e\u9802\uff0c\u4f46\u521d\u59cb\u5316\u4e0d\u6703\u3002\u56e0\u6b64\uff0c\u8b8a\u6578\u53ef\u4ee5\u5728\u5ba3\u544a\u4e4b\u524d\u4f7f\u7528\uff0c\u4f46\u503c\u6703\u662f undefined\u3002<\/p>\n
      \n
    1. \u51fd\u5f0f\u5ba3\u544a\u7684\u7f6e\u9802\uff1a<\/li>\n<\/ol>\n
      sayHello(); \/\/ \u8f38\u51fa\uff1a"Hello!"\n\nfunction sayHello() {\n    console.log("Hello!");\n}<\/code><\/pre>\n
      \u6574\u500b\u51fd\u5f0f\u5ba3\u544a\u90fd\u6703\u88ab\u7f6e\u9802\uff0c\u6240\u4ee5\u53ef\u4ee5\u5728\u5ba3\u544a\u4e4b\u524d\u547c\u53eb\u51fd\u5f0f\u3002<\/p>\n
        \n
      1. let \u548c const \u7684"\u66ab\u6642\u6027\u6b7b\u5340"\uff1a<\/li>\n<\/ol>\n
        console.log(x); \/\/ \u5831\u932f\uff1aCannot access 'x' before initialization\nlet x = 5;<\/code><\/pre>\n
        \u6280\u8853\u4e0a\uff0clet \u548c const \u4e5f\u6703\u88ab\u7f6e\u9802\uff0c\u4f46\u5b83\u5011\u4e0d\u6703\u50cf var \u90a3\u6a23\u88ab\u521d\u59cb\u5316\u70ba undefined\u3002\u5b83\u5011\u6703\u9032\u5165\u4e00\u500b"\u66ab\u6642\u6027\u6b7b\u5340"\uff0c\u5728\u90a3\u88e1\u5b83\u5011\u4e0d\u80fd\u88ab\u5b58\u53d6\u3002<\/p>\n
          \n
        1. \u51fd\u5f0f\u8868\u9054\u5f0f\u4e0d\u6703\u88ab\u7f6e\u9802\uff1a<\/li>\n<\/ol>\n
          sayHello(); \/\/ \u5831\u932f\uff1asayHello is not a function\n\nvar sayHello = function() {\n    console.log("Hello!");\n};<\/code><\/pre>\n
          \u53ea\u6709\u51fd\u5f0f\u5ba3\u544a\u6703\u88ab\u7f6e\u9802\uff0c\u51fd\u5f0f\u8868\u9054\u5f0f\u4e0d\u6703\u3002<\/p>\n
            \n
          1. \u7f6e\u9802\u7684\u512a\u5148\u9806\u5e8f\uff1a<\/li>\n<\/ol>\n
            var x = 1;\n\nfunction x() {\n    console.log("I am a function");\n}\n\nconsole.log(typeof x); \/\/ \u8f38\u51fa\uff1a"number"<\/code><\/pre>\n
            \u51fd\u5f0f\u5ba3\u544a\u7684\u7f6e\u9802\u512a\u5148\u65bc\u8b8a\u6578\u5ba3\u544a\uff0c\u4f46\u8b8a\u6578\u8ce6\u503c\u6703\u8986\u84cb\u51fd\u5f0f\u5ba3\u544a\u3002<\/p>\n
              \n
            1. \u5728\u5be6\u969b\u61c9\u7528\u4e2d\u907f\u514d\u4f9d\u8cf4\u7f6e\u9802\uff1a<\/li>\n<\/ol>\n
              \/\/ \u4e0d\u597d\u7684\u505a\u6cd5\nconsole.log(x);\nvar x = 5;\n\n\/\/ \u597d\u7684\u505a\u6cd5\nvar x;\nconsole.log(x);\nx = 5;<\/code><\/pre>\n
              \u96d6\u7136\u8b8a\u6578\u7f6e\u9802\u662f JavaScript \u7684\u4e00\u500b\u7279\u6027\uff0c\u4f46\u5728\u5be6\u969b\u7de8\u7a0b\u4e2d\uff0c\u6700\u597d\u907f\u514d\u4f9d\u8cf4\u5b83\uff0c\u56e0\u70ba\u9019\u53ef\u80fd\u5c0e\u81f4\u96e3\u4ee5\u7406\u89e3\u548c\u7dad\u8b77\u7684\u7a0b\u5f0f\u78bc\u3002<\/p>\n
              \u7406\u89e3\u8b8a\u6578\u7f6e\u9802\u5c0d\u65bc\u907f\u514d JavaScript \u4e2d\u7684\u4e00\u4e9b\u5e38\u898b\u932f\u8aa4\u975e\u5e38\u91cd\u8981\u3002\u5b83\u4e5f\u89e3\u91cb\u4e86\u70ba\u4ec0\u9ebc\u8a31\u591a JavaScript \u958b\u767c\u8005\u63a8\u85a6\u4f7f\u7528 let \u548c const \u800c\u4e0d\u662f var\uff0c\u56e0\u70ba\u5b83\u5011\u53ef\u4ee5\u5e6b\u52a9\u6211\u5011\u5beb\u51fa\u66f4\u53ef\u9810\u6e2c\u7684\u7a0b\u5f0f\u78bc\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
              JavaScript \u7684\u8b8a\u6578\u7f6e\u9802\uff08Variable Hoisting\uff09 \u8b8a\u6578\u7f6e\u9802 … <\/p>\n","protected":false},"author":1,"featured_media":14707,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_import_markdown_pro_load_document_selector":0,"_import_markdown_pro_submit_text_textarea":"","fifu_image_url":"","fifu_image_alt":"","footnotes":""},"categories":[266],"tags":[],"class_list":["post-15037","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-266"],"_links":{"self":[{"href":"https:\/\/fgchen.com\/wpedu\/wp-json\/wp\/v2\/posts\/15037","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fgchen.com\/wpedu\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/fgchen.com\/wpedu\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/fgchen.com\/wpedu\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fgchen.com\/wpedu\/wp-json\/wp\/v2\/comments?post=15037"}],"version-history":[{"count":1,"href":"https:\/\/fgchen.com\/wpedu\/wp-json\/wp\/v2\/posts\/15037\/revisions"}],"predecessor-version":[{"id":15038,"href":"https:\/\/fgchen.com\/wpedu\/wp-json\/wp\/v2\/posts\/15037\/revisions\/15038"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/fgchen.com\/wpedu\/wp-json\/wp\/v2\/media\/14707"}],"wp:attachment":[{"href":"https:\/\/fgchen.com\/wpedu\/wp-json\/wp\/v2\/media?parent=15037"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fgchen.com\/wpedu\/wp-json\/wp\/v2\/categories?post=15037"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fgchen.com\/wpedu\/wp-json\/wp\/v2\/tags?post=15037"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}