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Javascript 即使I'；我正在检查未定义的_Javascript - Fatal编程技术网
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Javascript 即使I'；我正在检查未定义的

javascript

Javascript 即使I'；我正在检查未定义的,javascript,Javascript,此代码： if(typeof(Listings.page_num) != 'undefined') { // something } 在firebug控制台中触发此通知： Listings is not defined http://mysite.com/js/content_ads.js Line 13 嗯，这就是我检查的原因！有没有办法摆脱这个通知？这样做 var Listings = Listings || {}; if (typeof Listings.page_num !==

此代码：

if(typeof(Listings.page_num) != 'undefined') {
   // something
}
在firebug控制台中触发此通知：

Listings is not defined http://mysite.com/js/content_ads.js Line 13
嗯，这就是我检查的原因！有没有办法摆脱这个通知？

这样做

var Listings = Listings || {};
if (typeof Listings.page_num !== "undefined") // page_num isset