How to check if a value is a number in JavaScript

Last updated on Mar 28, 2022 by Suraj Sharma

In this tutorial, you’ll learn two ways to check if a given value is a number in JavaScript

1. Using isNaN()

The isNaN() function determines whether the passed argument is NaN(not a number) or not.

It returns false if the passed argument is a number else returns true.


isNaN(45) // false
isNaN('Hello') // true
isNaN(NaN) // true
isNaN(45.02) // false
isNaN('45') // false

2. Using typeof operation

The typeof operator returns a string representing the type of a value/operand.


typeof 45 === 'number' // true
typeof 'hello' === 'number' // false
typeof 56.78 === 'number' // true

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Suraj Sharma is a Full Stack Software Engineer. He holds a B.Tech degree in Computer Science & Engineering from NIT Rourkela.