Adding and removing properties in Javascript

Introduction

We add or remove properties to change what information an object holds. This helps us update or clean up data easily.

When you want to add new details to an object, like adding a phone number to a contact.

When you need to remove outdated or wrong information from an object.

When building or modifying objects dynamically based on user input.

When cleaning up objects before sending data to a server.

When you want to customize objects by adding or removing features.

Syntax

Javascript

To add a property:
object.propertyName = value;

To remove a property:
delete object.propertyName;

You can add properties using dot notation or bracket notation.

Use delete keyword to remove a property from an object.

Examples

Adds a new property name with value 'Alice' to the person object.

Javascript

const person = {};
person.name = 'Alice';

Removes the brand property from the car object.

Javascript

const car = { brand: 'Toyota' };
delete car.brand;

Adds a property title using bracket notation.

Javascript

const book = {};
book['title'] = 'JavaScript Guide';

Sample Program

This program starts with a user object having username and age. It adds an email property and removes the age property. Finally, it prints the updated object.

Javascript

const user = {
  username: 'coder123',
  age: 25
};

// Add a new property
user.email = '[e-mail]';

// Remove the age property
delete user.age;

console.log(user);

Important Notes

Adding a property that already exists will update its value.

Removing a property that does not exist does nothing and does not cause errors.

Use bracket notation when property names have spaces or special characters.

Summary

You can add properties to objects using object.property = value.

Remove properties using delete object.property.

This helps keep objects up-to-date and clean.