The Number.isNaN()
method determines whether the passed value is NaN
and its type is Number
. It is a more robust version of the original, global isNaN()
.
Syntax
Number.isNaN(value)
Parameters
value
- The value to be tested for
NaN
.
Return value
true if the given value is NaN
and its type is Number
; otherwise, false.
Description
Due to both equality operators, ==
and ===
, evaluating to false
when checking if NaN
is NaN
, the function Number.isNaN()
has become necessary. This situation is unlike all other possible value comparisons in JavaScript.
In comparison to the global isNaN()
function, Number.isNaN()
doesn't suffer the problem of forcefully converting the parameter to a number. This means it is now safe to pass values that would normally convert to NaN
, but aren't actually the same value as NaN
. This also means that only values of the type number, that are also NaN
, return true
.
Polyfill
The following works because NaN is the only value in javascript which is not equal to itself.
Number.isNaN = Number.isNaN || function isNaN(input) { return typeof input === 'number' && input !== input; }
Examples
Using isNaN
Number.isNaN(NaN); // true Number.isNaN(Number.NaN); // true Number.isNaN(0 / 0); // true // e.g. these would have been true with global isNaN() Number.isNaN('NaN'); // false Number.isNaN(undefined); // false Number.isNaN({}); // false Number.isNaN('blabla'); // false // These all return false Number.isNaN(true); Number.isNaN(null); Number.isNaN(37); Number.isNaN('37'); Number.isNaN('37.37'); Number.isNaN(''); Number.isNaN(' ');
Specifications
Specification |
---|
ECMAScript (ECMA-262) The definition of 'Number.isnan' in that specification. |
Browser compatibility
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
isNaN | Chrome Full support 25 | Edge Full support 12 | Firefox Full support 15 | IE No support No | Opera Full support 15 | Safari Full support 9 | WebView Android Full support ≤37 | Chrome Android Full support 25 | Firefox Android Full support 15 | Opera Android Full support 14 | Safari iOS Full support 9 | Samsung Internet Android Full support 1.5 | nodejs Full support 0.10 |
Legend
- Full support
- Full support
- No support
- No support