{"id":12660,"date":"2023-11-28T23:02:39","date_gmt":"2023-11-28T15:02:39","guid":{"rendered":"https:\/\/wx.kaifamiao.info\/?p=12660"},"modified":"2023-11-28T23:17:12","modified_gmt":"2023-11-28T15:17:12","slug":"qian-duan-mian-shi-tivar-let-heconst-de-qu-bie-shi","status":"publish","type":"post","link":"http:\/\/wx.kaifamiao.info\/index.php\/2023\/11\/28\/qian-duan-mian-shi-tivar-let-heconst-de-qu-bie-shi\/","title":{"rendered":"\u524d\u7aef\u9762\u8bd5\u9898\uff1avar, let\u548cconst\u7684\u533a\u522b\u662f\u4ec0\u4e48\uff1f"},"content":{"rendered":"<p>var\u58f0\u660e\u7684\u53d8\u91cf\u4f1a\u6302\u8f7d\u5728window\u4e0a\uff0c\u800clet\u548cconst\u58f0\u660e\u7684\u53d8\u91cf\u4e0d\u4f1a\uff1a<br \/>\nvar a = 100\uff1b<br \/>\nconsole. log(a,window. a)\uff1b\t\/\/\t100 100<br \/>\nlet b = 10;<br \/>\nconsole. log(b,window. b)\uff1b\t\/\/\t10 undefined<br \/>\nconst c = 1;<br \/>\nconsole.log(c,window. c)\uff1b\t\/\/\t1 undefined<\/p>\n<p>var\u58f0\u660e\u53d8\u91cf\u5b58\u5728\u53d8\u91cf\u63d0\u5347\uff0clet\u548cconst\u4e0d\u5b58\u5728\u53d8\u91cf\u63d0\u5347\uff1a<br \/>\nconsole. log (a) \uff1b \/\/ undefined ===&gt; a \u5df2\u58f0\u660e\u8fd8\u6ca1\u8d4b\u503c\uff0c\u9ed8\u8ba4\u5f97\u5230 undefined \u503c var a = 100\uff1b console. log(b) \uff1b \/\/ \u62a5\u9519\uff1ab is not defined ==&gt; \u627e\u4e0d\u5230 b \u8fd9\u4e2a\u53d8\u91cf let b = 10\uff1b console. log(c) \uff1b \/\/ \u62a5\u9519\uff1ac is not defined ===&gt; \u627e\u4e0d\u5230 c \u8fd9\u4e2a\u53d8\u91cf const c = 10\uff1b let \u548cconst\u58f0\u660e\u5f62\u6210\u5757\u4f5c\u7528\u57df<br \/>\nif(l){<br \/>\nvar a = 100\uff1b<br \/>\nlet b = 10\uff1b<br \/>\n}<br \/>\nconsole. log(a)\uff1b \/\/ 100<br \/>\nconsole.log(b) \/\/ \u62a5\u9519\uff1ab is not defined =&gt; \u627e\u4e0d\u5230 b \u8fd9\u4e2a\u53d8\u91cf<br \/>\nif(l){<br \/>\nvar a = 100\uff1b<br \/>\n\u7b2c129\u9875<br \/>\n}<br \/>\nconsole. log(a)\uff1b \/\/ 100<br \/>\nconsole. log(c) \/\/ \u62a5\u9519\uff1ac is not defined =&gt; \u627e\u4e0d\u5230 c \u8fd9\u4e2a\u53d8\u91cf<br \/>\n\u540c\u4e00\u4f5c\u7528\u57df\u4e0blet\u548cconst\u4e0d\u80fd\u58f0\u660e\u540c\u540d\u53d8\u8463\uff0c\u800cvar\u53ef\u4ee5<br \/>\nvar a = 100\uff1b<br \/>\nconsole. log(a)\uff1b \/\/ 100<br \/>\nvar a = 10\uff1b<br \/>\nconsole. log(a)\uff1b \/\/ 10<br \/>\nlet a = 100\uff1b<br \/>\nlet a = 10\uff1b<br \/>\n\/\/ \u63a7\u5236\u53f0\u62a5\u9519\uff1aIdentifier &#8216; 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