JavaScript Instanceof Operator

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:

objectName: States the name of the Object.

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

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

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>