# Number.isInteger() – JavaScript

In JavaScript, `Number.isInteger()` method checks whether the passed value is an integer or not. The method `isInteger()` returns true if the provided value is an integer or type number. Otherwise, it returns false.

## Syntax

``````Number.isInteger(value)
``````

Parameters:

value – The `isInteger()` method accepts a single parameter value that needs to be tested, and its a required parameter

Return Value – The method `Number.isInteger()` returns a boolean value, i.e,. returns true if the target value passed is an integer. Otherwise, it returns false. If the value is `NaN `or `Infinity`, it returns false.

The `isInteger()` method returns true if you pass floating-point numbers that can be represented as an integer.

Let’s take few examples that illustrate the `Number.isInteger() `method in JavaScript.

## Passing positive number as an argument

If you pass a positive value to the function as an argument, then it returns true. If the value passed is not of integer type, then it returns false.

``console.log(Number.isInteger(77))``

Output

``true``

## Passing negative number as an argument

If you pass a negative value to the function as an argument, then it returns true. If the value passed is not of integer type, then it returns false.

``````console.log(Number.isInteger(-77))
console.log(Number.isInteger(-1.3))``````

Output

``````true
false``````

## Passing zero as an argument

If you pass zero as an argument to the `Number.isInteger()` method, it returns true as 0 is an valid integer.

``console.log(Number.isInteger(0))``

Output

``true``

## Passing floating-point number as an argument

If you pass a floating or decimal value to the function as an argument, it returns false as it’s not a valid integer.

``````console.log(Number.isInteger(34.33))
console.log(Number.isInteger(-1.4))``````

Output

``````flase
false``````

## Passing floating-point number as an argument representing integer format

If you pass a floating or decimal value representing an integer, the `isInteger()` method returns true as it can parse as a valid integer.

``````console.log(Number.isInteger(5.0)) //positive float representing as integer
console.log(Number.isInteger(5.0000000)) //positive float representing as integer
console.log(Number.isInteger(-12.0000000)) //negative float representing as integer
console.log(Number.isInteger(-5.000000000000001)) //negative float point number
console.log(Number.isInteger(-5.0000000000000001)) //negative float point number
console.log(Number.isInteger(-1.4))``````

Output

``````true
true
true
false
true
false``````

## Passing string as an argument

If you pass a string as an argument to the `Number.isInteger()` method, it will return false. Even if you pass integer in string format, the method will return false as it cannot parse the string value.

``````console.log(Number.isInteger('hello'))
console.log(Number.isInteger('55'))
``````

Output

``````false
false``````

## Passing NaN, Infinity, Boolean as an argument

If you pass a `NaN`, `Infinity`, `Boolean `as an argument to the `Number.isInteger() `method, it will return false.

``````console.log(Number.isInteger(NaN))
console.log(Number.isInteger(Infinity))
console.log(Number.isInteger(-Infinity))
console.log(Number.isInteger(true))
console.log(Number.isInteger(false))``````

Output

``````false
false
false
false
false``````

## Polyfill for Number.isInteger()

If you are looking for a Polyfill, you could use the code below if your browser is not supported.

``````Number.isInteger = Number.isInteger || function(value) {
return typeof value === 'number' &&
isFinite(value) &&
Math.floor(value) === value;
};``````

Supported Browsers:

• Edge: 12
• Internet Explorer: Not Supported
• Firefox: 16
• Apple Safari: 09
• Opera: 21

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