What is JavaScript Object isExtensible() Method?

In this article, we will learn JavaScript Object isExtensible() Method,This free Javascript tutorial for complete beginners will help you learn Javascript from scratch.

JavaScript Object isExtensible() Method

JavaScript Object is() Method

JavaScript Object isFrozen() Method

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:

obj: This parameter holds the object which should be checked for extensibility.

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 Beginner1 = {}; 
console.log(Object.isExtensible(Beginner1)); 
Object.preventExtensions(Beginner1); 
console.log(Object.isExtensible(Beginner1)); 
  
const Beginner2 = {}; 
Object.preventExtensions(Beginner2); 
console.log( 
    Object.isExtensible(Beginner2) 
);

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 Beginner1 = {}; 
console.log(Object.isExtensible(Beginner1)); 
console.log(Object.preventExtensions(Beginner1)); 
console.log(Object.isExtensible(Beginner1)); 
  
let Beginner2 = Object.seal({}); 
console.log(Object.isExtensible(Beginner2)); 
  
let Beginner3 = Object.freeze({}); 
console.log(Object.isExtensible(Beginner3));