Number.NaN

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

The Number.NaN static data property represents Not-A-Number, which is equivalent to NaN. For more information about the behaviors of NaN, see the description for the global property.

Try it

function clean(x) {
  if (x === Number.NaN) {
    // Can never be true
    return null;
  }
  if (isNaN(x)) {
    return 0;
  }
}

console.log(clean(Number.NaN));
// Expected output: 0

Value

The number value NaN.

Property attributes of Number.NaN

Writable	no
Enumerable	no
Configurable	no

Description

Because NaN is a static property of Number, you always use it as Number.NaN, rather than as a property of a number value.

Examples

Checking whether values are numeric

js
function sanitize(x) {
  if (isNaN(x)) {
    return Number.NaN;
  }
  return x;
}

Specifications

Specification

ECMAScript® 2027 Language Specification
# sec-number.nan

Browser compatibility

Enable JavaScript to view this browser compatibility table.

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This page was last modified on Jul 10, 2025 by MDN contributors.

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Standard built-in objects
Number
Constructor
1. Number()
Static methods
Static properties
Instance methods
Inheritance
Object/Function
Static methods
Static properties
Instance methods
Instance properties
1. __proto__
2. constructor