JavaScript Objects

JavaScript Fundamentals

JavaScript Objects

Beginner Lesson 5 of 10

JavaScript Objects

Objects are collections of key-value pairs that store related data and functionality.

Creating Objects

Object Literal

const person = {
  firstName: "John",
  lastName: "Doe",
  age: 30,
  fullName() {
    return `${this.firstName} ${this.lastName}`;
  }
};

Constructor Function

function Person(firstName, lastName) {
  this.firstName = firstName;
  this.lastName = lastName;
}

const john = new Person("John", "Doe");

ES6 Classes

class Person {
  constructor(firstName, lastName) {
    this.firstName = firstName;
    this.lastName = lastName;
  }

  fullName() {
    return `${this.firstName} ${this.lastName}`;
  }
}

const john = new Person("John", "Doe");

Accessing Properties

const person = { name: "Alice", age: 25 };

// Dot notation
person.name;      // "Alice"

// Bracket notation
person["age"];    // 25

// Destructuring
const { name, age } = person;

Object Methods

const obj = { a: 1, b: 2, c: 3 };

Object.keys(obj);    // ["a", "b", "c"]
Object.values(obj);  // [1, 2, 3]
Object.entries(obj); // [["a", 1], ["b", 2], ["c", 3]]

// Spread operator
const newObj = { ...obj, d: 4 };

// Object.assign
const merged = Object.assign({}, obj, { d: 4 });

Prototypes

function Animal(name) {
  this.name = name;
}

Animal.prototype.speak = function() {
  console.log(`${this.name} makes a sound`);
};

const dog = new Animal("Dog");
dog.speak(); // "Dog makes a sound"

Next Steps

Continue to Arrays →