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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.