How to use Object.freeze in JavaScript

Object.freeze is a handy tool that helps you make an object immutable in JavaScript.

Object.freeze(someObject);

If you try use the delete keyword or an assignment operator = after freezing the object with Object.freeze it will remain unchanged.

// declare the object
const frozenUser = {
  name: 'Jill',
  age: '22',
  isLearning: true
};

// freeze!
Object.freeze(frozenUser);

// an attemp to delete a propery and alter one
delete frozenUser.age;
frozenUser.isLearning = false;

// a proof that the object hasn't changed
console.log(frozenUser.name);  // John
console.log(frozenUser.age);  // 22
console.log(frozenUser.isLearning);  // true

Once we’ve applied Object.freeze to the frozenUser object, it became immutable. Neither the delete, nor the assignment operator = worked.