Data Structures

A data structure is a way of organizing data so it can be used effectively. JavaScript provides several built-in data structures, each suited to different kinds of problems.

Array

An array is an ordered list of values. You create one with square brackets, and you access elements by their numeric index:

var fruits = ["apple", "banana", "cherry"];
console.log(fruits[0]);       // apple
console.log(fruits.length);   // 3

Object

An object is a collection of key-value pairs. You can access values with dot notation or bracket notation:

var person = { name: "John", age: 30 };
console.log(person.name);   // John
console.log(person["age"]); // 30

Set

A Set stores unique values, so duplicates are automatically removed:

var numbers = new Set();
numbers.add(1);
numbers.add(2);
numbers.add(1);   // ignored, already present
console.log(numbers.size);  // 2

Map

A Map holds key-value pairs like an object, but keys can be any value (not just strings), and insertion order is preserved:

var scores = new Map();
scores.set("Alice", 90);
scores.set("Bob", 85);
console.log(scores.get("Alice"));  // 90

Exercise

1. Create an array called colors with the strings "red", "green", and "blue".
2. Create an object called fruit with a property name equal to "mango".
3. Print the first color, and print the fruit name.