JavaScript Object freeze() Method

The Object.freeze() method is used to freeze an object. Freezing an object does not allow new properties to be added to the object and prevents removing or altering the existing properties. Object.freeze() preserves the enumerability, configurability, writability, and prototype of the object. It returns the passed object and does not create a frozen copy.

Syntax:

Object.freeze(obj)

Parameters:

• obj: It is the object which has to be frozen.

Return Value: Object.freeze() returns the object that was passed to the function.

Examples of the above function are provided below.

Example 1: In this example, the object “obj2” has been assigned property from object “obj1”, and the properties of “obj1” are frozen therefore new properties and values are prevented from being added to “obj2”. 

Javascript

// creating an object constructor and assigning values to it
const obj1 = { property1: 'initial_data' };

// creating a second object which will freeze
// the properties of the first object
const obj2 = Object.freeze(obj1);

// Updating the properties of the frozen object
obj2.property1 = 'new_data';

// Displaying the properties of the  frozen object
console.log(obj2.property1);

Output :

"initial_data"

Example 2: In this example, the object “obj” has been assigned “prop: function” which has been later deleted since the object “obj wasn’t frozen. After that, a new object “o” has been assigned the frozen values of “obj” which prevented it from further updations.

Javascript

// creating an object constructor and assigning values to it
let obj = { prop: function () { }, name: 'adam' };

// Displaying the properties of the object created
console.log(obj);

// Updating the properties of the object
obj.name = 'billy';
delete obj.prop;
// Displaying the updated properties of the object
console.log(obj);

// Freezing the object using object.freeze() method
let o = Object.freeze(obj);

// Updating the properties of the frozen object
obj.name = 'chris';

// Displaying the properties of the  frozen object -->
console.log(obj);

Output :

Object { prop: function () {}, name: "adam" }
Object { name: "billy" }
Object { name: "billy" }

Applications:

• Object.freeze() is used for freezing objects and arrays, o make an object immutable.

We have a complete list of Javascript Object methods, to check those please go through this JavaScript Object Complete Reference article.

Supported Browsers:

• Google Chrome 6.0 and above
• Internet Explorer 9.0 and above
• Mozilla 4.0 and above
• Opera 11.1 and above
• Safari 5.0 and above