what is the reserved keyword for NaN in javascript?

Question

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?

Answer 1

Test if a value is NaN with the isNaN() function, appropriately enough. NaN is defined to be unequal to everything, including itself.

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For the sake of completeness:

• NaN is not a keyword, but is rather a built-in property of the global object, and as such may be replaced (like undefined, but unlike the keyword this or the literals true, false, and null).
• As "some" pointed out in the comments, there is also the global function isFinite() which may be useful.