JavaScript (ES2026) reference · Number Methods and Properties

JavaScript Number.isInteger() Method

Return true if a value is a number with no fractional part. Strings aren't converted, so Number.isInteger("5") is false.

JavaScript (ES2026) Since ES2015

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Syntax

Number.isInteger(value)

Parameter	Description
`value`	The value to test.

true or false.

Integers and non-integersTry it yourself

console.log(Number.isInteger(5), Number.isInteger(5.0), Number.isInteger(5.5), Number.isInteger("5"));

Output

true true false false

Validate a quantityTry it yourself

const qty = Number("3");
console.log(Number.isInteger(qty) && qty > 0 ? "valid quantity" : "invalid");

Output

valid quantity

Version	Change
JavaScript ES2015	Added

Number.isSafeInteger() · Return true if a value is an integer that can be represented exactly, between -(2^53 - 1) and 2^53 - 1.
Number.isFinite() · Return true if a value is a finite number. Unlike the global isFinite(), it doesn't convert strings.
JavaScript Numbers · tutorial
JavaScript Type Conversion · tutorial