testing for NaN

GitHub Brian Munoz

NaN, Not a Number, is returned when doing math operations with values that aren’t numbers.

NaN’s type is a number.

JavaScript

const division = 1 / 'e';

console.log(division); // NaN
console.log(typeof division); // number

When comparing NaN to itself it will always evaluate to false.

JavaScript

const division = 1 / 'e';

console.log(division === NaN); // false
console.log(division == NaN); // false

This could be used as a way to check if a value is NaN.

Number.isNaN() could also be used to check if a value is NaN.

JavaScript

const division = 1 / 'e';
const string = 'hi';

console.log(Number.isNaN(division)); // true
console.log(Number.isNaN(string)); // false

summary

When checking if a value is NaN use Number.isNaN().

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