JavaScript Number.NaN

The JavaScript Number.NaN property represents Not-A-Number. It is equivalent to NaN.

The syntax to access the NaN property is:

Number.NaN

NaN is accessed using the Number class name.


Example: Using Number.NaN

// verify value is a number
function verify(x) {
  if (isNaN(x)) {
    return Number.NaN;
  }
  return x; // only return if number is not NaN
}

console.log(verify(5)); // 5
console.log(verify(5.45)); // 5.45
console.log(verify(Infinity)); // Infinity

console.log(verify("five")); // NaN
console.log(verify(undefined)); // NaN
console.log(verify([1, 2, 3, 4])); // NaN

Output

5
5.45
Infinity
NaN
NaN
NaN

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