In JavaScript, why does isNaN(" ") evaluate to false, but isNaN(" x") evaluate to true? I’m performing numerical operations on a text input field, and I’m checking if the field is null, "", or NaN. When …

Oct 16, 2015 · Answer: Due to both equality operators, == and ===, evaluating to false when checking if NaN is NaN, the function Number.isNaN() has become necessary. In comparison to the global …

Apr 16, 2010 · var myVar = "A"; isNaN(Number(myVar)) // true. Number(myVar) is NaN here in fact It actually makes sense, because "A" is actually not a number. But what we really want to check is if …

Apr 23, 2015 · The function isNaN() can be used to answer this question, but semantically it's referring specifically to the value NaN. From Wikipedia for NaN: NaN (N ot a N umber) is a value of the …

While math.isnan and np.isnan will return True for NaN values, you cannot check for different type of objects like None or strings. Both methods will return an error, so checking a list with mixed types will …

Nov 11, 2015 · isNaN() returns false if and only if the argument is number. var a = new Number(1); By doing so, a is an object now. So why is isNaN(a) returning false?

goog.math.isFiniteNumber = function(num) { return isFinite(num) && !isNaN(num); }; So, first it checks whether the number is finite using the native isFinite function, and then does an additional check to …

Jul 10, 2017 · Number.isNaN only returns true if its argument is NaN. It seems weird, but the reason for its existence is falsiness of NaN === NaN expression.

Aug 7, 2014 · The reason isNaN() is "broken" is because, ostensibly, type conversions aren't supposed to happen when testing values. That is the issue Number.isNaN() is designed to address. In …

In case anyone else comes upon this, window.isNaN() will coerce a value into a number and THEN check if it is NaN. So undefined and "hello" will return true, while undefined and "" return false. This is …