Asked  7 Months ago    Answers:  5   Viewed   32 times

I’ve only been trying it in Firefox’s JavaScript console, but neither of the following statements return true:

parseFloat('geoff') == NaN;

parseFloat('geoff') == Number.NaN;



Try this code:


For checking whether any value is NaN, instead of just numbers, see here: How do you test for NaN in Javascript?

Tuesday, June 1, 2021
answered 7 Months ago

This worked for me:

$get("isAgeSelected ").checked == true

Where isAgeSelected is the id of the control.

Also, @karim79's answer works fine. I am not sure what I missed at the time I tested it.

Note, this is answer uses Microsoft Ajax, not jQuery

Tuesday, June 1, 2021
answered 7 Months ago

check for a remainder when dividing by 1:

function isInt(n) {
   return n % 1 === 0;

If you don't know that the argument is a number you need two tests:

function isInt(n){
    return Number(n) === n && n % 1 === 0;

function isFloat(n){
    return Number(n) === n && n % 1 !== 0;

Update 2019 5 years after this answer was written, a solution was standardized in ECMA Script 2015. That solution is covered in this answer.

Tuesday, June 1, 2021
answered 7 Months ago

NaN is not equal to anything, not even NaN.

Reference at MDN

More detailed SO question and answer

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.
Saturday, August 7, 2021
answered 4 Months ago

NaN is a primitive Number value. Just like 1, 2, etc.

Saturday, November 6, 2021
Elio Campitelli
answered 4 Weeks ago
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