You can do a strict comparison to the undefined value. if (x === undefined) { x = 0; }. Naturally you'll want to be sure that x has been ... ... <看更多>

区分JS中的undefined,null, ' ' ,0和false. ShenBao ·⊙· January 21, 2017 22:00:00. 分类： JavaScript. 由0 == ''结果是true思考，单独做了一下测试，记录于此。 ... <看更多>

null undefined NaN empty string ("") 0 false ... The set of "truthy" and "falsey" values in JavaScript comes from the ToBoolean abstract operation defined ... ... <看更多>

wkhtmltopdf version(s) affected: 0.12.5 OS information Ubuntu 16.04 Mac OS X 10.12.6 Description The following html/javascript throws (with ... ... <看更多>

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Summary: in this tutorial, you'll learn about the JavaScript undefined and how to ... let counter = { current: 0 }; console.log(counter.max); // undefined. ... <看更多>