JavaScript Object isExtensible() Method (original) (raw)

Last Updated : 29 May, 2023

The Object.preventExtensions() method in JavaScript is a standard built-in object which checks whether an object is extensible or not(i.e. if we can add new properties to the object or not).

Syntax:

Object.isExtensible( obj )

Parameters: This method accepts a single parameter as mentioned above and described below:

Return value: This method returns a Boolean value indicating if the given object is extensible or not.

The below examples illustrate the Object.isExtensible() Method in JavaScript:

Example 1: In this example, we will check if new properties can be added to an object or not using the Object.isExtensible() Method in JavaScript. The output is a Boolean value.

javascript `

const geeks1 = {}; console.log(Object.isExtensible(geeks1)); Object.preventExtensions(geeks1); console.log(Object.isExtensible(geeks1));

const geeks2 = {}; Object.preventExtensions(geeks2); console.log( Object.isExtensible(geeks2) );

`

Output:

true false false

Example 2: In this example, we will check if new properties can be added to an object or not using the Object.isExtensible() Method in JavaScript. The output is a Boolean value.

javascript `

let geeks1 = {}; console.log(Object.isExtensible(geeks1)); console.log(Object.preventExtensions(geeks1)); console.log(Object.isExtensible(geeks1));

let geeks2 = Object.seal({}); console.log(Object.isExtensible(geeks2));

let geeks3 = Object.freeze({}); console.log(Object.isExtensible(geeks3));

`

Output:

true [object Object] false false false

We have a complete list of Javascript Object methods, to check those please go through this JavaScript Object Complete Reference article.

Supported Browsers: The browsers supported by Object.isExtensible() method are listed below: