Number.isInteger() – JavaScript
Tags: javascript, programming, codenewbie, tutorial
Published: 2021-09-13 05:14:57

---
title: Number.isInteger() – JavaScript
published: true
date: 2021-09-12 09:42:36 UTC
tags: #JavaScript #programming #codenewbie #tutorial
canonical_url: https://itsmycode.com/number-isinteger-javascript/
---

ItsMyCode |

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

```JavaScript
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**.

```JavaScript
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**.

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

**Output**

```JavaScript
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.

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

**Output**

```JavaScript
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.

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

**Output**

```JavaScript
false
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.

```JavaScript
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**

```JavaScript
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.

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

```

**Output**

```JavaScript
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**.

```JavaScript
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**

```JavaScript
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.

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

**Supported Browsers:**

- **Google Chrome: 34**
- **Edge: 12**
- **Internet Explorer: Not Supported**
- **Firefox: 16**
- **Apple Safari: 09**
- **Opera: 21**

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