what is the reserved keyword for NaN in javascript?
javascript, nan
Solution
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).
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.
- As @some pointed out in the comments, there is also the global function isFinite() which may be useful.
Problem
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?