JavaScript Instanceof Operator (original) (raw)

Last Updated : 27 Dec, 2023

The **instanceof operator in JavaScript is used to check the type of an object at run time. It returns a boolean value if true then it indicates that the object is an instance of a particular class and if false then it is not.

**Syntax:

let gfg = objectName instanceof objectType

**Parameters:

**Return Value: This method returns a boolean value if true then it indicates that the object is an instance of a particular class and if false then it is not.

**Example 1: Below is the example of the Instanceof Operator.

html

<!DOCTYPE html>

< html lang = "en" >

< head >

`` < title >

`` How to Check/Uncheck the

`` checkbox using JavaScript ?

`` </ title >

</ head >

< body >

`` < h1 style = "color:green" >

`` GeeksforGeeks

`` </ h1 >

`` < h3 >

`` Instanceof Operator.

`` </ h3 >

`` < p id = "GFG" ></ p >

`` < script >

`` let a = ["Geeks", "for", "Geeks"];

`` document.getElementById("GFG").innerHTML =

`` (a instanceof Array) + "< br >" +

`` (a instanceof Number);

`` </ script >

</ body >

</ html >

**Output:

JavaScript Instanceof Operator

JavaScript Instanceof Operator

**Example 2: Below is the example of the Instanceof Operator.

html

<!DOCTYPE html>

< html lang = "en" >

< head >

`` < title >

`` How to Check/Uncheck the

`` checkbox using JavaScript ?

`` </ title >

</ head >

< body >

`` < h1 style = "color:green" >

`` GeeksforGeeks

`` </ h1 >

`` < h3 >

`` Instanceof Operator.

`` </ h3 >

`` < p id = "GFG" ></ p >

`` < script >

`` let fruits = ["Apple", "Mango", "Banana"];

`` document.getElementById("GFG").innerHTML =

`` (fruits instanceof Array) + "< br >" +

`` (fruits instanceof Object) + "< br >" +

`` (fruits instanceof String) + "< br >" +

`` (fruits instanceof Number);

`` </ script >

</ body >

</ html >

**Output:

JavaScript Instanceof Operator

JavaScript Instanceof Operator

**Example 3: Demonstrating that String and Date objects are also a type of Object (derived from Object).

Javascript

<script>

`` var myString = new String();

`` var myDate = new Date();

`` console.log(myString instanceof Object);

`` console.log(myString instanceof Date);

`` console.log(myString instanceof String);

`` console.log(myDate instanceof Date);

`` console.log(myDate instanceof Object);

`` console.log(myDate instanceof String);

</script>

**Output:

true
false
true
true
true
false

We have a complete list of Javascript Operators, to check those please go through the Javascript Operators Complete Reference article.

**Supported Browsers: