javascript - 为什么 angular.isNumber(NaN) 返回 true？

Question

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Answer 1

引用 IgorMinar , Angular Developer 在这个确切的 question :

$ node
> typeof NaN
'number'

It kind of makes sense if you squint with both eyes and plug your ears.

If you deliberately use NaN in your app, you should use isNaN instead of angular.isNumber.

I'm inclined to say that the current behavior, even though a bit surprising, is consistent with how NaN is being treated in javascript. If you have some good arguments for changing the behavior please share them with us.

所以问题真正针对的是 javascript 标准本身，而不是 Angular

要回答这个问题，我们必须转到 ECMAScript 5 specification of number type ，当然它说:

4.3.20 Number type

set of all possible Number values including the special “Not-a-Number” (NaN) values, positive infinity, and negative infinity

4.3.23 NaN

number value that is a IEEE 754 “Not-a-Number” value

所以是的，根据最新ECMAScript Specification我是一个数字