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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.

Example 1: Is 578 an Integer?

Number.isInteger(578);

// The invocation above will return: true

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Example 2: Is 0.99 an Integer?

Number.isInteger(0.99);

// The invocation above will return: false

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Example 3: Is "test" an Integer?

Number.isInteger("test");

// The invocation above will return: false

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Example 4: Is Negative 300 an Integer?

Number.isInteger(-300);

// The invocation above will return: true

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Example 5: Is Zero an Integer?

Number.isInteger(0);

// The invocation above will return: true

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Example 6: Is Math.PI an Integer?

Number.isInteger(Math.PI);

// The invocation above will return: false

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Overview

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