Object Protection

Object Protection Methods

// Prevents re-assignment
const car = {type:“Fiat”, model:“500”, color:“white”};

// Prevents adding object properties
Object.preventExtensions(object)

// Returns true if properties can be added to an object
Object.isExtensible(object)

// Prevents adding and deleting object properties
Object.seal(object)

// Returns true if object is sealed
Object.isSealed(object)

// Prevents any changes to an object
Object.freeze(object)

// Returns true if object is frozen
Object.isFrozen(object)

Since arrays are objects, they can also be prevented from being extended.

Example

// Create Array
const fruits = [“Banana”, “Orange”, “Apple”, “Mango”];
Object.preventExtensions(fruits);

// This will throw an error:
fruits.push(“Kiwi”);

JavaScript Object.isExtensible()

You can use Object.isExtensible() to determine if an object is extensible.

The Object.isExtensible() method returns true if the object is extensible.

Examples

// Create Object
const person = {firstName:“John”, lastName:“Doe”};

// Prevent Extensions
Object.preventExtensions(person);

// This will return false
let answer = Object.isExtensible(person);

// Create Array
const fruits = [“Banana”, “Orange”, “Apple”, “Mango”];

// Prevent Extensions
Object.preventExtensions(fruits);

// This will return false
let answer = Object.isExtensible(fruits);