?? JavaScript Maps

A Map in JavaScript is a collection of key-value pairs where:

• Keys can be any data type (objects, functions, primitives)

• Keys maintain the insertion order

• Maps are iterable

Why use a Map instead of a plain object?

• Objects only allow strings and symbols as keys

• Maps allow any type as a key (e.g., objects, functions)

• Maps have a size property (easy to get the number of entries)

• Maps are designed specifically for mapping key-value pairs with useful built-in methods

Creating a Map

const map = new Map();

Or initialize with an array of key-value pairs:

const map = new Map([  ['name', 'Alice'],  ['age', 25]]);

Basic Operations

const map = new Map();// Add entriesmap.set('name', 'Bob');map.set(42, 'The answer');map.set(true, 'Yes');// Get valuesconsole.log(map.get('name'));  // Bobconsole.log(map.get(42));      // The answer// Check if key existsconsole.log(map.has(true));    // true// Size of mapconsole.log(map.size);         // 3// Delete an entrymap.delete(42);// Clear all entries// map.clear();

Iterating over a Map

for (const [key, value] of map) {  console.log(`${key} => ${value}`);}

Map vs Object

Want a practical example using Maps, or help converting Maps to arrays/objects?