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JavaScript | Object.isExtensible() Method

  • Last Updated : 17 Sep, 2021

The Object.preventExtensions() method in JavaScript is standard built-in objects which checks whether an object is extensible or not.
Syntax: 
 

Object.isExtensible( obj )

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

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

Return value: This method returns a Boolean value indicating if the given object is extensible or not.
Below examples illustrate the Object.isExtensible() Method in JavaScript:
Example 1: 
 

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: 
 



javascript




var geeks1 = {};
document.writeln(Object.isExtensible(geeks1));
document.writeln("<br>");
document.writeln(Object.preventExtensions(geeks1));
document.writeln("<br>");
document.writeln(Object.isExtensible(geeks1));
document.writeln("<br>");
 
var geeks2 = Object.seal({});
document.writeln(Object.isExtensible(geeks2));
document.writeln("<br>");
 
var geeks3 = Object.freeze({});
document.writeln(Object.isExtensible(geeks3));

Output: 
 

true
[object Object]
false
false
false

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

  • Google Chrome 6 and above
  • Edge 12 and above
  • Firefox 4 and above
  • Internet Explorer 9
  • Opera 12 and above
  • Safari 5.1 and above

 

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