{"id":584,"date":"2017-02-26T11:05:15","date_gmt":"2017-02-26T03:05:15","guid":{"rendered":"http:\/\/www.qdabc.cn\/?p=584"},"modified":"2017-02-26T11:05:15","modified_gmt":"2017-02-26T03:05:15","slug":"js%e4%b8%adconstvarlet%e4%b9%8b%e9%97%b4%e7%9a%84%e5%8c%ba%e5%88%ab","status":"publish","type":"post","link":"http:\/\/www.qdabc.cn\/?p=584","title":{"rendered":"js\u4e2dconst,var,let\u4e4b\u95f4\u7684\u533a\u522b"},"content":{"rendered":"<p>js\u4e2d\u4e09\u79cd\u5b9a\u4e49\u53d8\u91cf\u7684\u65b9\u5f0fconst\uff0c var\uff0c let\u7684\u533a\u522b\u3002let\u662fES6\u4e2d\u7684\u58f0\u660e\u53d8\u91cf<\/p>\n<p>1.const\u5b9a\u4e49\u7684\u53d8\u91cf\u4e0d\u53ef\u4ee5\u4fee\u6539\uff0c\u800c\u4e14\u5fc5\u987b\u521d\u59cb\u5316\u3002<\/p>\n<pre class=\"brush:js;toolbar:false\">const b = 2;\/\/\u6b63\u786e\r\n\/\/ const b;\/\/\u9519\u8bef\uff0c\u5fc5\u987b\u521d\u59cb\u5316 \r\nconsole.log('\u51fd\u6570\u5916const\u5b9a\u4e49b\uff1a' + b);\/\/\u6709\u8f93\u51fa\u503c\r\n\/\/ b = 5;\r\n\/\/ console.log('\u51fd\u6570\u5916\u4fee\u6539const\u5b9a\u4e49b\uff1a' + b);\/\/\u65e0\u6cd5\u8f93\u51fa<\/pre>\n<p>2.var\u5b9a\u4e49\u7684\u53d8\u91cf\u53ef\u4ee5\u4fee\u6539\uff0c\u5982\u679c\u4e0d\u521d\u59cb\u5316\u4f1a\u8f93\u51faundefined\uff0c\u4e0d\u4f1a\u62a5\u9519\u3002<\/p>\n<pre class=\"brush:js;toolbar:false\">var a = 1;\r\n\/\/ var a;\/\/\u4e0d\u4f1a\u62a5\u9519\r\nconsole.log('\u51fd\u6570\u5916var\u5b9a\u4e49a\uff1a' + a);\/\/\u53ef\u4ee5\u8f93\u51faa=1\r\nfunction change(){\r\n    a = 4;\r\n    console.log('\u51fd\u6570\u5185var\u5b9a\u4e49a\uff1a' + a);\/\/\u53ef\u4ee5\u8f93\u51faa=4\r\n} \r\nchange();\r\nconsole.log('\u51fd\u6570\u8c03\u7528\u540evar\u5b9a\u4e49a\u4e3a\u51fd\u6570\u5185\u90e8\u4fee\u6539\u503c\uff1a' + a);\/\/\u53ef\u4ee5\u8f93\u51faa=4<\/pre>\n<p>3.let\u662f\u5757\u7ea7\u4f5c\u7528\u57df\uff0c\u51fd\u6570\u5185\u90e8\u4f7f\u7528let\u5b9a\u4e49\u540e\uff0c\u5bf9\u51fd\u6570\u5916\u90e8\u65e0\u5f71\u54cd\u3002<\/p>\n<pre class=\"brush:js;toolbar:false\">let c = 3;\r\nconsole.log('\u51fd\u6570\u5916let\u5b9a\u4e49c\uff1a' + c);\/\/\u8f93\u51fac=3\r\nfunction change(){\r\n    let c = 6;\r\n    console.log('\u51fd\u6570\u5185let\u5b9a\u4e49c\uff1a' + c);\/\/\u8f93\u51fac=6\r\n} \r\nchange();\r\nconsole.log('\u51fd\u6570\u8c03\u7528\u540elet\u5b9a\u4e49c\u4e0d\u53d7\u51fd\u6570\u5185\u90e8\u5b9a\u4e49\u5f71\u54cd\uff1a' + c);\/\/\u8f93\u51fac=3<\/pre>\n<p class=\"post-copyright\">\u6b22\u8fce\u5206\u4eab\u672c\u6587\uff0c\u8f6c\u8f7d\u8bf7\u4fdd\u7559\u51fa\u5904\uff1a<a href=\"http:\/\/www.qdabc.cn\">\u524d\u7aefABC<\/a> &raquo; <a href=\"http:\/\/www.qdabc.cn\/?p=584\">js\u4e2dconst,var,let\u4e4b\u95f4\u7684\u533a\u522b<\/a><\/p>","protected":false},"excerpt":{"rendered":"<p>js\u4e2d\u4e09\u79cd\u5b9a\u4e49\u53d8\u91cf\u7684\u65b9\u5f0fconst\uff0c var\uff0c let\u7684\u533a\u522b\u3002let\u662fES6\u4e2d\u7684\u58f0\u660e\u53d8\u91cf 1.const\u5b9a\u4e49\u7684\u53d8\u91cf\u4e0d\u53ef\u4ee5\u4fee\u6539\uff0c\u800c\u4e14\u5fc5\u987b\u521d\u59cb\u5316\u3002 const b = 2;\/\/\u6b63\u786e \/\/ const b; [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":90,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[153,9,155,154],"_links":{"self":[{"href":"http:\/\/www.qdabc.cn\/index.php?rest_route=\/wp\/v2\/posts\/584"}],"collection":[{"href":"http:\/\/www.qdabc.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.qdabc.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.qdabc.cn\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.qdabc.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=584"}],"version-history":[{"count":1,"href":"http:\/\/www.qdabc.cn\/index.php?rest_route=\/wp\/v2\/posts\/584\/revisions"}],"predecessor-version":[{"id":585,"href":"http:\/\/www.qdabc.cn\/index.php?rest_route=\/wp\/v2\/posts\/584\/revisions\/585"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/www.qdabc.cn\/index.php?rest_route=\/wp\/v2\/media\/90"}],"wp:attachment":[{"href":"http:\/\/www.qdabc.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=584"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.qdabc.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=584"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.qdabc.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=584"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}