Javascript变量/'NaN'表现异常 [英] Javascript variable / 'NaN' behaving weirdly

问题描述

我有几个文本框，如果文本框中包含有效数据，则返回javascript Number值，否则返回NaN.我得到这种奇怪的行为.当我签入firebug时(两个文本框均为空白):

I have a couple of textboxes, Which return javascript Number values if valid data is in the textboxes, otherwise NaN. I get this strange behavior. When I checked in firebug (both the textboxes are blank):

>>> hours
NaN
>>> minutes
NaN
>>> minutes == NaN
false
>>> hours == NaN
false
>>> hours == minutes
false

为什么会这样?

推荐答案

NaN不等于任何东西，甚至不等于NaN.

NaN is not equal to anything, not even NaN.

在MDN上的引用

更详细的SO问答

有关权威信息，请参见 ECMAScript 5官方规范 ， 11.9.1 和 11.9.3 :

For the authoritative source, see the ECMAScript 5 Official Specification, sections 11.9.1 and 11.9.3:

1. If Type(x) is the same as Type(y), then
     [...]
  c. If Type(x) is Number, then
     i. If x is NaN, return false.
    ii. If y is NaN, return false.
        [...]

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