NaN global property JS Home  <<  JS Reference  <<  NaN

Global property that represents the value Not-A-Number.

Description

NaN is returned from functions where parsing to a number fails or from Math functions where a numeric result can't be derived or is unobtainable.

  • The NaN global property is also unique in JavaScript in the fact that you cannot rely on the equality (==) and strict equality (===) comparison operators to find out whether a value is NaN or not. For this reason we have the isNaN() global function which we can use to determine whether a value is NaN or not.

Syntax

Signature Description
NaNGlobal property that represents the value Not-A-Number.

Parameters

None.

Below are some examples showing comparisons of NaN and an unobtainable result.


// NaN.
var nanValues = new Array(4);

nanValues[0] = NaN == NaN; // NaN not equal
nanValues[1] = NaN === NaN; // NaN not strict
nanValues[2] = isNaN(NaN); // check against isNaN
nanValues[3] = Number.POSITIVE_INFINITY * 0; // unobtainable 

alert(nanValues);

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Related Tutorials

JavaScript Intermediate Tutorials - Lesson 6 - More Maths Functions