Number.NaN is the Not-A-Number value — the same IEEE-754 NaN as global NaN. It marks an invalid numeric result. It is a static property, not a method, and it never equals itself with ===.
Read the notes below before you rely on this property. Prefer feature detection when support is limited.
Use Number.NaN. Start with this line.
Number.NaN| Call | What it does |
|---|---|
Number.NaN | Primary signature. |
Built into JavaScript. Read Number.NaN on the Number constructor — no import required.
Number.NaNThis member has no parameters beyond those shown in the signature.
| Return Value | Description |
|---|---|
| * | The current value of Number.NaN. |
Number.NaNPrint the constant and confirm it matches global NaN.
console.log(Number.NaN);
console.log(Object.is(Number.NaN, NaN));Number.NaN on the constructor — there is no (5).NaN.Object.is confirms it is the same as global NaN.=== cannot prove sameness for NaN — more on that next.NaN is the only value that is not equal to itself.
console.log(Number.NaN === Number.NaN); // false
console.log(0 / 0 === Number.NaN); // false
console.log(Number.isNaN(0 / 0)); // trueNumber.NaN === Number.NaN is always false.0 / 0 is NaN, but === Number.NaN still fails.Number.isNaN(0 / 0) returns true.===.isNaN vs Number.isNaNGlobal isNaN coerces; Number.isNaN does not.
console.log(Number.isNaN(Number.NaN)); // true
console.log(Number.isNaN("foo")); // false
console.log(isNaN("foo")); // true — coerces!Number.isNaN(Number.NaN) is true.Number.isNaN("foo") is false.isNaN("foo") converts to NaN first → true.Number.isNaN in new code to avoid string traps.Number.NaN is part of core JavaScript and is Baseline Widely available in modern browsers and Node.js.
Supported in Chrome, Firefox, Safari, Edge, and Node.js for decades. Same value as global NaN.
Bottom line: Use Number.NaN freely. Pair it with Number.isNaN (ES2015) for reliable detection in modern apps.
Learn how to create Number values and convert strings to numbers.
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