JS107 - Arrays & Objects Basics

Arrays and objects are the most commonly used data structures in JavaScript.
They allow you to store multiple values and organize your data effectively.

Arrays

An array stores a list of values.
Values can be numbers, strings, objects, or even other arrays.

let numbers = [1, 2, 3, 4];
let fruits = ["apple", "banana", "orange"];

Accessing array items:

console.log(fruits[0]); // apple
console.log(fruits[2]); // orange

Updating array items:

fruits[1] = "kiwi";

Array Methods

JavaScript includes many built-in methods.

let items = ["a", "b", "c"];
 
items.push("d");      // ["a", "b", "c", "d"]
items.pop();            // removes last item
items.shift();          // removes first item
items.unshift("z");   // adds to the beginning

Modern array helpers:

items.forEach(item => console.log(item));
 
let uppercased = items.map(item => item.toUpperCase());
 
let filtered = items.filter(item => item !== "b");

Objects

Objects store data in key-value pairs.

let user = {
  name: "Emre",
  age: 30,
  city: "Antalya"
};

Accessing values:

console.log(user.name);
console.log(user['city']);

Updating properties:

user.age = 31;
user.country = "Turkey";

Nested Objects and Arrays

Objects can contain arrays and arrays can contain objects.

let product = {
  title: "Phone",
  price: 12000,
  colors: ["black", "white"],
  seller: {
    name: "TechStore",
    rating: 4.8
  }
};

Accessing nested values:

console.log(product.colors[1]);     // white
console.log(product.seller.name);    // TechStore

Object Methods

Objects can also contain functions.

let person = {
  name: "Emre",
  greet() {
    console.log("Hello, " + this.name);
  }
};
 
person.greet(); // Hello, Emre

Destructuring (ES6)

Destructuring allows you to extract values quickly.

let {name, city} = user;
console.log(name); // Emre

Array destructuring:

let [first, second] = fruits;

Spread Operator

let extended = [...numbers, 5, 6];
let clonedUser = {...user};

Spread makes copying and merging easy.

Summary

In this lesson, you learned:

How arrays store ordered lists
Common array methods
How objects store key-value pairs
Nested objects and arrays
Object methods and this keyword
Destructuring and spread operator

In the next lesson, we will explore loops and iteration to work efficiently with lists of data.