{"id":4009,"date":"2024-11-10T17:54:54","date_gmt":"2024-11-10T09:54:54","guid":{"rendered":"https:\/\/fwq.ai\/blog\/4009\/"},"modified":"2024-11-10T17:54:54","modified_gmt":"2024-11-10T09:54:54","slug":"javascript-%e4%b8%ad-var-%e5%92%8c-let-%e5%8f%98%e9%87%8f%e5%a3%b0%e6%98%8e%e6%9c%89%e4%bb%80%e4%b9%88%e5%8c%ba%e5%88%ab%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/fwq.ai\/blog\/4009\/","title":{"rendered":"JavaScript \u4e2d var \u548c let \u53d8\u91cf\u58f0\u660e\u6709\u4ec0\u4e48\u533a\u522b\uff1f"},"content":{"rendered":"<p><img decoding=\"async\" src=\"https:\/\/img.php.cn\/upload\/article\/001\/246\/273\/173121138312152.jpg\" class=\"aligncenter\" title=\"JavaScript \u4e2d var \u548c let \u53d8\u91cf\u58f0\u660e\u6709\u4ec0\u4e48\u533a\u522b\uff1f\u63d2\u56fe\" alt=\"JavaScript \u4e2d var \u548c let \u53d8\u91cf\u58f0\u660e\u6709\u4ec0\u4e48\u533a\u522b\uff1f\u63d2\u56fe\" \/><\/p>\n<p><strong>javascript \u4e2d var \u548c let \u53d8\u91cf\u58f0\u660e\u7684\u5dee\u5f02<\/strong><\/p>\n<p>\u5728 javascript \u4e2d\uff0c\u53ef\u4ee5\u58f0\u660e\u53d8\u91cf\u7684\u65b9\u5f0f\u6709\u4e24\u79cd\uff1avar \u548c let\u3002\u5b83\u4eec\u4e4b\u95f4\u7684\u4e3b\u8981\u5728\u4e8e\u3002<\/p>\n<p><strong>var<\/strong><\/p>\n<ul>\n<li>\u4f7f\u7528 var \u58f0\u660e\u7684\u53d8\u91cf\u5c5e\u4e8e\u5168\u5c40\u53d8\u91cf\u3002<\/li>\n<li>\u53d8\u91cf\u53ef\u4ee5\u591a\u6b21\u58f0\u660e\uff0c\u5e76\u4e14\u6bcf\u6b21\u58f0\u660e\u90fd\u4f1a\u521b\u5efa\u65b0\u7684\u53d8\u91cf\u3002<\/li>\n<li>\u53d8\u91cf\u53ef\u4ee5\u5728\u58f0\u660e\u4e4b\u524d\u8bbf\u95ee\uff0c\u8fd9\u4f1a\u5bfc\u81f4\u4e00\u4e2a\u540d\u4e3a\u201c\u53d8\u91cf\u63d0\u5347\u201d\u7684\u884c\u4e3a\u3002<\/li>\n<\/ul>\n<pre>var i = 0;\nconsole.log(i); \/\/ \u8f93\u51fa\uff1aundefined\ni = 1;\nconsole.log(i); \/\/ \u8f93\u51fa\uff1a1<\/pre>\n<p> \u767b\u5f55\u540e\u590d\u5236 <\/p>\n<p><strong>let<\/strong><\/p>\n<p><span>\u7acb\u5373\u5b66\u4e60<\/span>\u201c\u201d\uff1b<\/p>\n<ul>\n<li>\u4f7f\u7528 let \u58f0\u660e\u7684\u53d8\u91cf\u662f\u5c40\u90e8\u53d8\u91cf\u3002<\/li>\n<li>\u53d8\u91cf\u53ea\u80fd\u58f0\u660e\u4e00\u6b21\uff0c\u5426\u5219\u4f1a\u629b\u51fa\u9519\u8bef\u3002<\/li>\n<li>\u53d8\u91cf\u53ea\u80fd\u5728\u58f0\u660e\u4e4b\u540e\u8bbf\u95ee\uff0c\u56e0\u6b64\u4e0d\u4f1a\u51fa\u73b0\u201c\u53d8\u91cf\u63d0\u5347\u201d\u884c\u4e3a\u3002<\/li>\n<\/ul>\n<pre>let i = 0;\nconsole.log(i); \/\/ \u8f93\u51fa\uff1a0\ni = 1;\nconsole.log(i); \/\/ \u8f93\u51fa\uff1a1<\/pre>\n<p> \u767b\u5f55\u540e\u590d\u5236 <\/p>\n<p>\u9664\u4e86 let \u4e4b\u5916\uff0c\u8fd8\u6709\u4e00\u79cd\u79f0\u4e3a const \u7684\u53d8\u91cf\u58f0\u660e\u65b9\u5f0f\u3002const \u58f0\u660e\u7684\u53d8\u91cf\u4e5f\u662f\u5c40\u90e8\u53d8\u91cf\uff0c\u4f46\u5b83\u4eec\u7684\u503c\u4e0d\u80fd\u88ab\u66f4\u6539\u3002<\/p>\n<p>\u603b\u800c\u8a00\u4e4b\uff0cvar \u58f0\u660e\u5168\u5c40\u53d8\u91cf\uff0clet \u548c const \u58f0\u660e\u5c40\u90e8\u53d8\u91cf\u3002let \u548c const \u53ef\u4ee5\u9632\u6b62\u53d8\u91cf\u63d0\u5347\uff0c\u5e76\u4e14 let \u5141\u8bb8\u4fee\u6539\u53d8\u91cf\u7684\u503c\uff0c\u800c const \u5219\u4e0d\u5141\u8bb8\u3002<\/p>\n<p>\u4ee5\u4e0a\u5c31\u662fJavaScript \u4e2d var \u548c let \u53d8\u91cf\u58f0\u660e\u6709\u4ec0\u4e48\uff1f\u7684\u8be6\u7ec6\u5185\u5bb9\uff0c\u66f4\u591a\u8bf7\u5173\u6ce8\u7c73\u4e91\u5176\u5b83\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"<p>javascript \u4e2d var \u548c let \u53d8\u91cf\u58f0\u660e\u7684\u5dee\u5f02 \u5728 javascript \u4e2d\uff0c\u53ef\u4ee5\u58f0\u660e\u53d8\u91cf\u7684\u65b9\u5f0f\u6709\u4e24\u79cd\uff1avar \u548c let\u3002\u5b83\u4eec\u4e4b\u95f4\u7684\u4e3b\u8981\u5728\u4e8e\u3002 var \u4f7f\u7528 var \u58f0\u660e\u7684\u53d8\u91cf\u5c5e\u4e8e\u5168\u5c40\u53d8\u91cf\u3002 \u53d8\u91cf\u53ef\u4ee5\u591a\u6b21\u58f0\u660e\uff0c\u5e76\u4e14\u6bcf\u6b21\u58f0\u660e\u90fd\u4f1a\u521b\u5efa\u65b0\u7684\u53d8\u91cf\u3002 \u53d8\u91cf\u53ef\u4ee5\u5728\u58f0\u660e\u4e4b\u524d\u8bbf\u95ee\uff0c\u8fd9\u4f1a\u5bfc\u81f4\u4e00\u4e2a\u540d\u4e3a\u201c\u53d8\u91cf\u63d0\u5347\u201d\u7684\u884c\u4e3a\u3002 var i = 0; console.log(i); \/\/ \u8f93\u51fa\uff1aundefined i = 1; console.log(i); \/\/ \u8f93\u51fa\uff1a1 \u767b\u5f55\u540e\u590d\u5236 let \u7acb\u5373\u5b66\u4e60\u201c\u201d\uff1b \u4f7f\u7528 let \u58f0\u660e\u7684\u53d8\u91cf\u662f\u5c40\u90e8\u53d8\u91cf\u3002 \u53d8\u91cf\u53ea\u80fd\u58f0\u660e\u4e00\u6b21\uff0c\u5426\u5219\u4f1a\u629b\u51fa\u9519\u8bef\u3002 \u53d8\u91cf\u53ea\u80fd\u5728\u58f0\u660e\u4e4b\u540e\u8bbf\u95ee\uff0c\u56e0\u6b64\u4e0d\u4f1a\u51fa\u73b0\u201c\u53d8\u91cf\u63d0\u5347\u201d\u884c\u4e3a\u3002 let i = 0; console.log(i); \/\/ \u8f93\u51fa\uff1a0 i = 1; console.log(i); \/\/ \u8f93\u51fa\uff1a1 \u767b\u5f55\u540e\u590d\u5236 \u9664\u4e86 let \u4e4b\u5916\uff0c\u8fd8\u6709\u4e00\u79cd\u79f0\u4e3a [&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-4009","post","type-post","status-publish","format-standard","hentry","category-16"],"_links":{"self":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/4009","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=4009"}],"version-history":[{"count":0,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/4009\/revisions"}],"wp:attachment":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/media?parent=4009"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/categories?post=4009"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/tags?post=4009"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}