It is possible to make a non extensible object extensible ?

var obj = {};
Object.preventExtensions(obj);
obj.abc = "abc"; // this line is ignored which is normal
//is there a way to make obj extensible again

It is possible to make a non extensible object extensible ?

var obj = {};
Object.preventExtensions(obj);
obj.abc = "abc"; // this line is ignored which is normal
//is there a way to make obj extensible again

• javascript
• object
• properties

Share Improve this question Follow edited Sep 11, 2018 at 11:15 jenson-button-event 19k1313 gold badges9696 silver badges163163 bronze badges asked Oct 17, 2016 at 14:34 SAADSAAD 32244 silver badges1010 bronze badges 1

• 1 On MDN web docs it says "There is no way to make an object extensible again once it has been made non-extensible." Maybe you could reassign the object? – Todd Commented May 21, 2018 at 21:39

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2 Answers 2

Sorted by: Reset to default 5

How about a deep clone?

obj = JSON.parse(JSON.stringify(obj));
obj.abc = "abc"; // this line is now OK

Is OK in local code but any external references that came with obj will no longer point to the newly formed obj.

As MDN says:

There is no way to make an object extensible again once it has been made non-extensible.

The easiest way to overe this situation is to clone the object and assign it to a new variable:

const person = {
  name: "John",
  colors: {
    eyes: 'orange',
    hair: 'blue'
  }
};

Object.preventExtensions(person);
console.log(Object.isExtensible(person)); // false

const extensiblePerson = {...person};
console.log(Object.isExtensible(extensiblePerson)); // true

It is important to note that Object.preventExtensions only prevents the extension of the top level of the object. In the example above, person.colors is still extensible, even though its parent object is not.

console.log(Object.isExtensible(person.colors)); // true
console.log(extensiblePerson.colors === person.colors); // true