{"id":4907,"date":"2024-12-30T16:27:23","date_gmt":"2024-12-30T08:27:23","guid":{"rendered":"https:\/\/qaqaq.top\/?p=4907"},"modified":"2024-12-30T16:27:23","modified_gmt":"2024-12-30T08:27:23","slug":"%e5%b7%a5%e4%bd%9c%e6%97%b6%e9%81%87%e5%88%b0%e7%9a%84%e4%b8%80%e4%ba%9b%e5%b0%8f%e9%97%ae%e9%a2%98-2024-javascript","status":"publish","type":"post","link":"https:\/\/qaqaq.top\/?p=4907","title":{"rendered":"\u5de5\u4f5c\u65f6\u9047\u5230\u7684\u4e00\u4e9b\u5c0f\u95ee\u9898 2024-JavaScript"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\">JavaScript\uff1a\u5168\u5c40\u53d8\u91cf\u53d6\u7a7a\u95ee\u9898<\/h2>\n\n\n\n<h4 class=\"wp-block-heading\">\u4ee3\u7801<\/h4>\n\n\n\n<pre class=\"wp-block-preformatted\">    var searchCode = search;<\/pre>\n\n\n\n<h4 class=\"wp-block-heading\">\u7ed3\u679c<\/h4>\n\n\n\n<p>\u4f1a\u629b\u51fa\u5f02\u5e38<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u539f\u56e0<\/h4>\n\n\n\n<p>\u5728JavaScript\u4e2d\uff0c\u8981\u5224\u65ad\u4e00\u4e2a\u5168\u5c40\u53d8\u91cf\u662f\u5426\u5b58\u5728\uff08\u5373\u662f\u5426\u5df2\u7ecf\u88ab\u5b9a\u4e49\uff09\uff0c\u53ef\u4ee5\u4f7f\u7528 <code>typeof<\/code> \u8fd0\u7b97\u7b26\u3002\u5982\u679c\u4e00\u4e2a\u53d8\u91cf\u672a\u88ab\u5b9a\u4e49\uff0c<code>typeof<\/code> \u8fd0\u7b97\u7b26\u4f1a\u8fd4\u56de <code>\"undefined\"<\/code>\u3002<\/p>\n\n\n\n<p>\u4e0b\u9762\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u793a\u4f8b\uff0c\u5c55\u793a\u4e86\u5982\u4f55\u68c0\u67e5\u4e00\u4e2a\u5168\u5c40\u53d8\u91cf\u662f\u5426\u5b58\u5728\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">\/\/ \u5047\u8bbe\u6211\u4eec\u8981\u68c0\u67e5\u7684\u5168\u5c40\u53d8\u91cf\u540d\u4e3a myGlobalVariable<br>\u200b<br>\/\/ \u68c0\u67e5\u53d8\u91cf\u662f\u5426\u5b58\u5728<br>if (typeof myGlobalVariable === 'undefined') {<br> &nbsp; &nbsp;console.log('myGlobalVariable does not exist.');<br>} else {<br> &nbsp; &nbsp;console.log('myGlobalVariable exists and its value is:', myGlobalVariable);<br>}<\/pre>\n\n\n\n<h4 class=\"wp-block-heading\">\u89e3\u51b3<\/h4>\n\n\n\n<pre class=\"wp-block-preformatted\">if (typeof search != 'undefined') {<br>    var searchCode = search;<br>}<\/pre>\n\n\n\n<h4 class=\"wp-block-heading\">\u6ce8\u610f<\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u5728\u4f7f\u7528 <code>typeof<\/code> \u8fd0\u7b97\u7b26\u68c0\u67e5\u53d8\u91cf\u4e4b\u524d\uff0c\u786e\u4fdd\u4e0d\u8981\u58f0\u660e\u8be5\u53d8\u91cf\uff0c\u5426\u5219\u68c0\u67e5\u5c06\u59cb\u7ec8\u8fd4\u56de <code>true<\/code>\u3002<\/li>\n\n\n\n<li>\u5f53\u68c0\u67e5\u5168\u5c40\u53d8\u91cf\u65f6\uff0c\u786e\u4fdd\u4f7f\u7528\u7684\u5168\u5c40\u5bf9\u8c61\uff08\u5982 <code>window<\/code> \u6216 <code>global<\/code>\uff09\u4e0e\u8fd0\u884c\u73af\u5883\u76f8\u7b26\u3002<\/li>\n\n\n\n<li>\u5982\u679c\u4e0d\u786e\u5b9a\u5168\u5c40\u53d8\u91cf\u662f\u5426\u88ab\u5176\u4ed6\u811a\u672c\u5b9a\u4e49\uff0c\u53ef\u4ee5\u4f7f\u7528 <code>try...catch<\/code> \u7ed3\u6784\u6765\u6355\u83b7\u53ef\u80fd\u629b\u51fa\u7684\u5f02\u5e38\u3002<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>JavaScript\uff1a\u5168\u5c40\u53d8\u91cf\u53d6\u7a7a\u95ee\u9898 \u4ee3\u7801 var searchCode = search; \u7ed3\u679c \u4f1a\u629b\u51fa\u5f02 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[187],"tags":[189],"class_list":["post-4907","post","type-post","status-publish","format-standard","hentry","category-react-","tag-react"],"_links":{"self":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/4907"}],"collection":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=4907"}],"version-history":[{"count":1,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/4907\/revisions"}],"predecessor-version":[{"id":4908,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/4907\/revisions\/4908"}],"wp:attachment":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=4907"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=4907"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=4907"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}