Skip to content

The Object freeze() method

New Courses Coming Soon

Join the waiting lists

Find out all about the JavaScript freeze() method of the Object object

The JavaScript freeze() method of the Object object takes an object as argument, and returns the same object. The object passed as argument is mutated and it’s now an immutable object. No properties can be added, no properties can be removed, properties can’t be changed.


const dog = {}
dog.breed = 'Siberian Husky'
const myDog = Object.freeze(dog)

Object.isFrozen(dog) //true
Object.isFrozen(myDog) //true
dog === myDog //true = 'Roger' //TypeError: Cannot add property name, object is not extensible

Also see Object.isFrozen()

In the example, both dog and myDog are frozen. The argument passed as argument to Object.freeze() is mutated, and can’t be un-freezed. It’s also returned as argument, hence dog === myDog (it’s the same exact object).

Calling Object.freeze() is the equivalent of calling Object.preventExtensions() to prevent an object to have more properties defined, plus setting all properties as non-configurable and non-writeable.

→ Get my JavaScript Beginner's Handbook
→ Read my JavaScript Tutorials on The Valley of Code
→ Read my TypeScript Tutorial on The Valley of Code

Here is how can I help you: