{"id":52484,"date":"2024-12-03T13:14:08","date_gmt":"2024-12-03T05:14:08","guid":{"rendered":"https:\/\/fwq.ai\/blog\/52484\/"},"modified":"2024-12-03T13:14:08","modified_gmt":"2024-12-03T05:14:08","slug":"javascript-%e4%b8%ad-var-%e5%92%8c-let-%e6%9c%89%e4%bb%80%e4%b9%88%e5%8c%ba%e5%88%ab%ef%bc%9f-2","status":"publish","type":"post","link":"https:\/\/fwq.ai\/blog\/52484\/","title":{"rendered":"JavaScript \u4e2d var \u548c let \u6709\u4ec0\u4e48\u533a\u522b\uff1f"},"content":{"rendered":"<p><b><\/b>     <\/p>\n<h1>JavaScript \u4e2d var \u548c let \u6709\u4ec0\u4e48\u533a\u522b\uff1f<\/h1>\n<p>\u4eb2\u7231\u7684\u7f16\u7a0b\u5b66\u4e60\u7231\u597d\u8005\uff0c\u5982\u679c\u4f60\u70b9\u5f00\u4e86\u8fd9\u7bc7\u6587\u7ae0\uff0c\u8bf4\u660e\u4f60\u5bf9\u300aJavaScript \u4e2d var \u548c let \u6709\u4ec0\u4e48\u533a\u522b\uff1f\u300b\u5f88\u611f\u5174\u8da3\u3002\u672c\u7bc7\u6587\u7ae0\u5c31\u6765\u7ed9\u5927\u5bb6\u8be6\u7ec6\u89e3\u6790\u4e00\u4e0b\uff0c\u4e3b\u8981\u4ecb\u7ecd\u4e00\u4e0b\uff0c\u5e0c\u671b\u6240\u6709\u8ba4\u771f\u8bfb\u5b8c\u7684\u7ae5\u978b\u4eec\uff0c\u90fd\u6709\u5b9e\u8d28\u6027\u7684\u63d0\u9ad8\u3002<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/www.17golang.com\/uploads\/20241120\/1732112679673df1274b23f.jpg\" class=\"aligncenter\" title=\"JavaScript \u4e2d var \u548c let \u6709\u4ec0\u4e48\u533a\u522b\uff1f\u63d2\u56fe\" alt=\"JavaScript \u4e2d var \u548c let \u6709\u4ec0\u4e48\u533a\u522b\uff1f\u63d2\u56fe\" \/><\/p>\n<p><strong>javascript \u4e2d var \u548c let \u7684\u533a\u522b<\/strong><\/p>\n<p>\u5728 javascript \u4e2d\uff0c\u4f7f\u7528 var \u548c let \u5173\u952e\u5b57\u53ef\u4ee5\u58f0\u660e\u548c\u5b9a\u4e49\u53d8\u91cf\u3002\u7136\u800c\uff0c\u8fd9\u4e24\u4e2a\u5173\u952e\u5b57\u4e4b\u95f4\u5b58\u5728\u7740\u4e00\u4e9b\u5173\u952e\u7684\u533a\u522b\uff1a<\/p>\n<p><strong>\u4f5c\u7528\u57df<\/strong><\/p>\n<ul>\n<li><strong>var\uff1a<\/strong>\u58f0\u660e\u7684\u53d8\u91cf\u5177\u6709\u5168\u5c40\u4f5c\u7528\u57df\uff0c\u8fd9\u610f\u5473\u7740\u53ef\u4ee5\u5728\u4ee3\u7801\u7684\u4efb\u4f55\u4f4d\u7f6e\u8bbf\u95ee\u8fd9\u4e9b\u53d8\u91cf\u3002<\/li>\n<li><strong>let\uff1a<\/strong>\u58f0\u660e\u7684\u53d8\u91cf\u5177\u6709\u5c40\u90e8\u4f5c\u7528\u57df\uff0c\u8fd9\u610f\u5473\u7740\u53ea\u80fd\u5728\u5b9a\u4e49\u5b83\u4eec\u7684\u5757\u5185\u8bbf\u95ee\u8fd9\u4e9b\u53d8\u91cf\u3002<\/li>\n<\/ul>\n<p><strong>\u91cd\u65b0\u58f0\u660e<\/strong><\/p>\n<ul>\n<li><strong>var\uff1a<\/strong>\u53ef\u4ee5\u591a\u6b21\u91cd\u65b0\u58f0\u660e\uff08\u4f46\u5728\u540c\u4e00\u4f5c\u7528\u57df\u5185\uff09\u5177\u6709\u76f8\u540c\u540d\u79f0\u7684\u53d8\u91cf\u3002<\/li>\n<li><strong>let\uff1a<\/strong>\u5728\u540c\u4e00\u4f5c\u7528\u57df\u5185\u91cd\u590d\u58f0\u660e\u5177\u6709\u76f8\u540c\u540d\u79f0\u7684\u53d8\u91cf\u4f1a\u62a5\u9519\u3002<\/li>\n<\/ul>\n<p><strong>\u91cd\u65b0\u8d4b\u503c<\/strong><\/p>\n<ul>\n<li><strong>var\uff1a<\/strong>\u58f0\u660e\u7684\u53d8\u91cf\u53ef\u4ee5\u88ab\u91cd\u65b0\u8d4b\u503c\u3002<\/li>\n<li><strong>let\uff1a<\/strong>\u58f0\u660e\u7684\u53d8\u91cf\u4e5f\u53ef\u4ee5\u88ab\u91cd\u65b0\u8d4b\u503c\u3002<\/li>\n<\/ul>\n<p><strong>\u5e38\u91cf<\/strong><\/p>\n<p>javascript \u8fd8\u63d0\u4f9b\u4e86\u4e00\u4e2a const \u5173\u952e\u5b57\uff0c\u7528\u4e8e\u58f0\u660e\u5e38\u91cf\u53d8\u91cf\u3002\u5e38\u91cf\u53d8\u91cf\u4e0d\u80fd\u88ab\u91cd\u65b0\u8d4b\u503c\uff0c\u5e76\u4e14\u5177\u6709\u4e0e let \u76f8\u540c\u7684\u4f5c\u7528\u57df\uff08\u5373\u5c40\u90e8\uff09\u3002<\/p>\n<p>\u4ee5\u4e0b\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u793a\u4f8b\uff0c\u6765\u8bf4\u660e var \u548c let \u4e4b\u95f4\u7684\u533a\u522b\uff1a<\/p>\n<pre>\/\/ \u4f7f\u7528 var \u58f0\u660e\u5168\u5c40\u53d8\u91cf\nvar x = 10;\n\n\/\/ \u5728\u51fd\u6570\u5185\u4f7f\u7528 var \u58f0\u660e\u5c40\u90e8\u53d8\u91cf\nfunction test() {\n  var y = 20;\n  console.log(x); \/\/ 10\uff08\u8bbf\u95ee\u5168\u5c40\u53d8\u91cf\uff09\n  console.log(y); \/\/ 20\uff08\u8bbf\u95ee\u5c40\u90e8\u53d8\u91cf\uff09\n}\n\ntest();\n\n\/\/ \u5728\u51fd\u6570\u5916\u8bbf\u95ee\u5c40\u90e8\u53d8\u91cf\u5c06\u5bfc\u81f4\u9519\u8bef\nconsole.log(y); \/\/ referenceerror: y is not defined<\/pre>\n<p>\u800c\u5728\u4ee5\u4e0b\u793a\u4f8b\u4e2d\uff0c\u4f7f\u7528 let \u58f0\u660e\u5c40\u90e8\u53d8\u91cf\uff1a<\/p>\n<pre>\/\/ \u4f7f\u7528 let \u58f0\u660e\u5c40\u90e8\u53d8\u91cf\nfunction test() {\n  let x = 10; \/\/ \u5c40\u90e8\u53d8\u91cf x\n  console.log(x); \/\/ 10\n}\n\ntest();\n\n\/\/ \u5728\u51fd\u6570\u5916\u8bbf\u95ee\u5c40\u90e8\u53d8\u91cf\u5c06\u5bfc\u81f4\u9519\u8bef\nconsole.log(x); \/\/ ReferenceError: x is not defined<\/pre>\n<p>\u5728\u8fd9\u4e2a\u793a\u4f8b\u4e2d\uff0c\u51fd\u6570 test() \u5185\u58f0\u660e\u7684\u53d8\u91cf x \u4ec5\u5728\u8be5\u51fd\u6570\u5185\u53ef\u7528\uff0c\u800c\u5728\u51fd\u6570\u5916\u90e8\u8bbf\u95ee\u8be5\u53d8\u91cf\u4f1a\u5f15\u53d1\u9519\u8bef\u3002<\/p>\n<p>\u672c\u7bc7\u5173\u4e8e\u300aJavaScript \u4e2d var \u548c let \u6709\u4ec0\u4e48\u533a\u522b\uff1f\u300b\u7684\u4ecb\u7ecd\u5c31\u5230\u6b64\u7ed3\u675f\u5566\uff0c\u4f46\u662f\u5b66\u65e0\u6b62\u5883\uff0c\u60f3\u8981\u4e86\u89e3\u5b66\u4e60\u66f4\u591a\u5173\u4e8e\u6587\u7ae0\u7684\u76f8\u5173\u77e5\u8bc6\uff0c\u8bf7\u5173\u6ce8\u7c73\u4e91\u516c\u4f17\u53f7\uff01<\/p>\n<dl>\n<dt><\/dt>\n<dd>\n   \u63ed\u79d8\u7535\u8111\u5185\u5b58\uff1a\u4ece\u8fd0\u884c\u901f\u5ea6\u5230\u9009\u8d2d\u6307\u5357\n <\/dd>\n<\/dl>\n","protected":false},"excerpt":{"rendered":"<p>JavaScript \u4e2d var \u548c let \u6709\u4ec0\u4e48\u533a\u522b\uff1f \u4eb2\u7231\u7684\u7f16\u7a0b\u5b66\u4e60\u7231\u597d\u8005\uff0c\u5982\u679c\u4f60\u70b9\u5f00\u4e86\u8fd9\u7bc7\u6587\u7ae0\uff0c\u8bf4\u660e\u4f60\u5bf9\u300aJavaScript \u4e2d var \u548c let \u6709\u4ec0\u4e48\u533a\u522b\uff1f\u300b\u5f88\u611f\u5174\u8da3\u3002\u672c\u7bc7\u6587\u7ae0\u5c31\u6765\u7ed9\u5927\u5bb6\u8be6\u7ec6\u89e3\u6790\u4e00\u4e0b\uff0c\u4e3b\u8981\u4ecb\u7ecd\u4e00\u4e0b\uff0c\u5e0c\u671b\u6240\u6709\u8ba4\u771f\u8bfb\u5b8c\u7684\u7ae5\u978b\u4eec\uff0c\u90fd\u6709\u5b9e\u8d28\u6027\u7684\u63d0\u9ad8\u3002 javascript \u4e2d var \u548c let \u7684\u533a\u522b \u5728 javascript \u4e2d\uff0c\u4f7f\u7528 var \u548c let \u5173\u952e\u5b57\u53ef\u4ee5\u58f0\u660e\u548c\u5b9a\u4e49\u53d8\u91cf\u3002\u7136\u800c\uff0c\u8fd9\u4e24\u4e2a\u5173\u952e\u5b57\u4e4b\u95f4\u5b58\u5728\u7740\u4e00\u4e9b\u5173\u952e\u7684\u533a\u522b\uff1a \u4f5c\u7528\u57df var\uff1a\u58f0\u660e\u7684\u53d8\u91cf\u5177\u6709\u5168\u5c40\u4f5c\u7528\u57df\uff0c\u8fd9\u610f\u5473\u7740\u53ef\u4ee5\u5728\u4ee3\u7801\u7684\u4efb\u4f55\u4f4d\u7f6e\u8bbf\u95ee\u8fd9\u4e9b\u53d8\u91cf\u3002 let\uff1a\u58f0\u660e\u7684\u53d8\u91cf\u5177\u6709\u5c40\u90e8\u4f5c\u7528\u57df\uff0c\u8fd9\u610f\u5473\u7740\u53ea\u80fd\u5728\u5b9a\u4e49\u5b83\u4eec\u7684\u5757\u5185\u8bbf\u95ee\u8fd9\u4e9b\u53d8\u91cf\u3002 \u91cd\u65b0\u58f0\u660e var\uff1a\u53ef\u4ee5\u591a\u6b21\u91cd\u65b0\u58f0\u660e\uff08\u4f46\u5728\u540c\u4e00\u4f5c\u7528\u57df\u5185\uff09\u5177\u6709\u76f8\u540c\u540d\u79f0\u7684\u53d8\u91cf\u3002 let\uff1a\u5728\u540c\u4e00\u4f5c\u7528\u57df\u5185\u91cd\u590d\u58f0\u660e\u5177\u6709\u76f8\u540c\u540d\u79f0\u7684\u53d8\u91cf\u4f1a\u62a5\u9519\u3002 \u91cd\u65b0\u8d4b\u503c var\uff1a\u58f0\u660e\u7684\u53d8\u91cf\u53ef\u4ee5\u88ab\u91cd\u65b0\u8d4b\u503c\u3002 let\uff1a\u58f0\u660e\u7684\u53d8\u91cf\u4e5f\u53ef\u4ee5\u88ab\u91cd\u65b0\u8d4b\u503c\u3002 \u5e38\u91cf javascript \u8fd8\u63d0\u4f9b\u4e86\u4e00\u4e2a const \u5173\u952e\u5b57\uff0c\u7528\u4e8e\u58f0\u660e\u5e38\u91cf\u53d8\u91cf\u3002\u5e38\u91cf\u53d8\u91cf\u4e0d\u80fd\u88ab\u91cd\u65b0\u8d4b\u503c\uff0c\u5e76\u4e14\u5177\u6709\u4e0e let \u76f8\u540c\u7684\u4f5c\u7528\u57df\uff08\u5373\u5c40\u90e8\uff09\u3002 \u4ee5\u4e0b\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u793a\u4f8b\uff0c\u6765\u8bf4\u660e var \u548c let \u4e4b\u95f4\u7684\u533a\u522b\uff1a \/\/ \u4f7f\u7528 var \u58f0\u660e\u5168\u5c40\u53d8\u91cf var x = 10; \/\/ [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16],"tags":[],"class_list":["post-52484","post","type-post","status-publish","format-standard","hentry","category-16"],"_links":{"self":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/52484","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/comments?post=52484"}],"version-history":[{"count":0,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/52484\/revisions"}],"wp:attachment":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/media?parent=52484"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/categories?post=52484"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/tags?post=52484"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}