javascript中NaN的保留关键字是什么？ [英] what is the reserved keyword for NaN in javascript?

问题描述

如果我想测试表达式的结果并且该函数将返回NaN
我将如何检查？

示例：
$（' amount'）。value.toInt（）！='NaN'
^不起作用，我假设返回的值不是字符串，

$（'amount'）。value.toInt（）！= NaN
^似乎也没有工作，这个看起来很明显

b $ b
so我如何检查返回值是否为数字？

if i want to test the result of an expression and the function would return NaN how would i check that?
examples:
$('amount').value.toInt()!='NaN'
^ does not work and i assume that the returned value is not a string,
$('amount').value.toInt()!=NaN
^ doesnt seem to work either and this one seems obvious

so how do i check wether the returned value is not a number?

推荐答案

NaN值定义为不等于所有内容，包括本身。使用 <$ c $测试值是否为NaN c> isNaN（） 功能，足够恰当。 （ECMAScript 6添加了 Number.isNan（） 函数具有非数字参数的不同语义，但从2015年起在所有浏览器中都不支持。）

The NaN value is defined to be unequal to everything, including itself. Test if a value is NaN with the isNaN() function, appropriately enough. (ECMAScript 6 adds a Number.isNan() function with different semantics for non-number arguments, but it's not supported in all browsers yet as of 2015).

有两个内置属性可用，具有NaN值：全局 NaN 属性（即浏览器中的 window.NaN ），以及 Number.NaN 。它不是 语言关键字。在旧版浏览器中， NaN 属性可能会被覆盖，结果可能会令人困惑，但 ECMAScript 5标准它是不可写的。

There are two built-in properties available with a NaN value: the global NaN property (i.e. window.NaN in browsers), and Number.NaN. It is not a language keyword. In older browsers, the NaN property could be overwritten, with potentially confusing results, but with the ECMAScript 5 standard it was made non-writable.

• 正如@some在评论中指出的那样，还有全局函数 isFinite（）可能有用。

• As @some pointed out in the comments, there is also the global function isFinite() which may be useful.

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