你如何在JavaScript中测试NaN？ [英] How do you test for NaN in JavaScript?

问题描述

我有一个变量x，我想测试x是否设置为NaN。我该怎么做？

I have a variable x and I want to test if x is set to NaN. How do I do that?

我的第一直觉可能就是测试它，就像这样：

My first instinct is probably to, you know, test it, like this:

if (x === NaN) {  ...

<傻兔子，不，那太容易了。 NaN在SQL中就像NULL，它不等于任何东西，甚至本身。

Silly rabbit, no, that would be far too easy. NaN is like NULL in SQL, it is not equal to anything, even itself.

但是看，有一个名为的函数isNaN（） - 也许会这样做！

But look, there is a function called isNaN() -- maybe that will do it!

不，据我所知， isNaN（）完全没用。

No, so far as I can tell, isNaN() is utterly worthless.

例如， isNaN（[]）正确返回false，但是 isNaN（[。]）返回true。你不想知道我是如何了解这个漏洞的。

For example, isNaN([""]) properly returns false, but isNaN(["."]) returns true. You don't want do know how I learned about this flaw.

我该怎么做？

事实证明，我的问题与这个重复一个，但选择的答案是错误的。 正确答案的赞成数量为20％。

Turns out, my question is a duplicate of this one, but the selected answer is wrong. The right answer has 20% as many upvotes.

推荐答案

如果你仔细阅读，这个问题就有答案了。这就是我发现它的方式：我正在输入问题并且... bingo。

The question has the answer if you read closely enough. That is the way I found it: I was typing out the question and... bingo.

你还记得当我写 NaN 在SQL中就像NULL，它不等于任何东西，甚至本身？据我所知， NaN 是Javascript中唯一具有此属性的值。因此你可以写：

You remember when I wrote "NaN is like NULL in SQL, it is not equal to anything, even itself"? So far as I know, NaN is the only value in Javascript with this property. Therefore you can write:

var reallyIsNaN = function(x) {
   return x !== x;
};

这篇关于你如何在JavaScript中测试NaN？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！