JavaScript · Quick Reference

Lesson 9 — Objects Cheat Sheet

JavaScript

In one line: An object is a collection of key-value pairs. Keys are strings (or Symbols), and values can be any data type.

Key Ideas

1Object Literals & Property Access. An object is a collection of key-value pairs. Keys are strings (or Symbols), and values can be any data type.

2Methods & The this Keyword. Object methods are functions stored as property values. Inside a method, this refers to the object the method belongs to.

Code Examples

// Object literal
const user = {
  name: 'Ali',
  age: 25,
  email: 'ali@example.com',
  isAdmin: false
};

// Dot notation (preferred when key is known)
user.name;         // 'Ali'
user.age;          // 25

// Bracket notation (when key is dyna...

const person = {
  name: 'Sara',
  age: 28,
  // Method using regular function (this works!)
  greet() {
    return `Hello, I'm ${this.name}!`;
  },
  getInfo() {
    return `${this.name} is ${this.age} years old.`;
  },
  haveBirthday() {
    th...

const product = {
  id: 42,
  name: 'Keyboard',
  price: 75,
  brand: 'Logitech'
};

// Basic destructuring
const { name, price } = product;
// name='Keyboard', price=75

// Rename while destructuring
const { name: productName, price: cost } = p...