Skip to main content

Number.isInteger() – How to Check If a Number Is an Integer

Number.isInteger() checks if its argument is an integer. If so, it returns true. Otherwise, the method returns false.

Syntax of the Number.isInteger() Method​

Number.isInteger() accepts only one required argument. Here is the syntax:

Number.isInteger(value);

The value argument represents the item you wish to test if it is an integer.

note
  • Integers are numbers without decimals. In other words, an integer can be negative, zero, or positive numbers. However, they do not include fractions (decimals).
  • Some decimal numbers suffer from loss of precision in JavaScript. Therefore, Number.isInteger() will return true for numbers like 5.0000000000000001 and 4500000000000000.1.

Examples of the Number.isInteger() Method​

Below are examples of the Number.isInteger() method.

Is 578 an integer?​

Number.isInteger(578);

// The invocation above will return: true

Try Editing It

Is 0.99 an integer?​

Number.isInteger(0.99);

// The invocation above will return: false

Try Editing It

Is "test" an integer?​

Number.isInteger("test");

// The invocation above will return: false

Try Editing It

Is negative 300 an integer?​

Number.isInteger(-300);

// The invocation above will return: true

Try Editing It

Is zero an integer?​

Number.isInteger(0);

// The invocation above will return: true

Try Editing It

Is Math.PI an integer?​

Number.isInteger(Math.PI);

// The invocation above will return: false

Try Editing It

Overview​

This article discussed what Number.isInteger() is. We also used examples to see how it works.