如何测试某些东西是否与NaN相同？ [英] How to test whether something is identically NaN?

问题描述

在Javascript中：

In Javascript:

NaN === NaN; // false

我试图确定何时 isNaN（foo）不仅仅等于 + foo 是 NaN 。但是我不知道如何判断某些东西是否是 NaN ，除非使用 isNaN ，这对许多事情都是肯定的，其中没有 === NaN。

I was trying to determine when isNaN(foo) is not just equivalent to +foo "is" NaN. But I don't know how to tell if something is NaN except by using isNaN, which says yes for many things, none of which === NaN.

所以我认为正确的方法是工作围绕其他可能性：

So I think the right way to do this would be to work around other possibilities:

typeof NaN === 'number' // true

因此我认为

typeof(foo) === 'number' && isNaN(foo)

最接近我的想法。这是有道理的，因为 NaN 是唯一不是数字或其他东西的数字。这是正确的，这是最好的方法吗？

Is the closest to what I am thinking of. It makes sense since it makes sense that NaN would be the only number that isn't a number, or something. Is this correct, and is this the best way?

推荐答案

利用这个优势：

foo !== foo

这相当于 typeof foo ==='number'&& isNaN（foo），是Underscore.js用于检查确切 NaN 的内容。

This is equivalent to typeof foo === 'number' && isNaN(foo), and is what Underscore.js uses to check for exactly NaN, too.

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