JavaScript: Check for integer values using the isInteger() method

Posted on Apr 01, 2022

Learn how to check for integer values in JavaScript with the isInteger() method


JavaScript Number object comes with the isInteger() method that you can use to check if the passed argument is a whole number (integer).

The method accepts one parameter: the value to be tested if it’s an integer.

If the argument is an integer, the method returns true. Otherwise, it returns false:

console.log(Number.isInteger(10)); // true

let name = "Nathan";
console.log(Number.isInteger(name)); // false

Any number you passed with floating points will return false.

So do NaN, Infinity, and the boolean values:

let float = 6.873

console.log(Number.isInteger(float)); // false
console.log(Number.isInteger(0.12)); // false

console.log(Number.isInteger(NaN)); // false
console.log(Number.isInteger(Infinity)); // false

console.log(Number.isInteger(true)); // false
console.log(Number.isInteger(false)); // false

The method only returns true when you pass a whole number as its argument.

Any floating numbers that can be represented as integers will also return true, such as 1.0, 2.0, and so on:

console.log(Number.isInteger(1)); // true
console.log(Number.isInteger(2)); // true
console.log(Number.isInteger(2.0)); // true
console.log(Number.isInteger(59.0)); // true

console.log(Number.isInteger([1, 2, 4])); // false

And that’s how the Number.isInteger() method works in JavaScript.

You can use this method whenever you need to check if a value is an integer or not.

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