Course Lessons
Lesson 3 of 3
Arrays and Objects
Learn to work with JavaScript's most important data structures: arrays for lists and objects for structured data.
28 minutes
Arrays and Objects
Arrays and objects are fundamental data structures in JavaScript.
Arrays
Arrays store ordered collections of items:
- Access items by index (starting at 0)
- Use methods like
push(),pop(),map(),filter() - Perfect for lists of similar items
Objects
Objects store key-value pairs:
- Access properties with dot notation or brackets
- Can contain any data type as values
- Perfect for structured data
Array Methods
- map(): Transform each item
- filter(): Keep items that match a condition
- reduce(): Combine all items into one value
- find(): Get first item matching a condition
Destructuring
Modern JavaScript lets you unpack values easily from arrays and objects.
Code Example
// Arrays
const fruits = ["apple", "banana", "orange"];
fruits.push("grape");
const doubled = [1, 2, 3].map(n => n * 2);
console.log(doubled); // [2, 4, 6]
// Objects
const user = {
name: "Elena",
age: 28,
skills: ["JavaScript", "React", "Node.js"]
};
console.log(user.name); // Elena
console.log(user.skills[0]); // JavaScript
// Destructuring
const { name, age } = user;
const [first, second] = fruits;