JavaScript Maps

JavaScript Maps

A Map holds key-value pairs, like an object but with useful extra features.

Creating a Map

const users = new Map([
  ["ada", 36],
  ["bob", 40]
]);

Add a pair

users.set("carol", 25);

Get a value

users.get("ada"); // 36

Check a key

users.has("bob"); // true

Remove a pair

users.delete("bob");

Size

users.size;

Map vs Object

• Map keys can be ANY type (objects, numbers, functions).
• Map has a reliable .size property.
• Maps are easy to iterate in insertion order.
• Objects have literal syntax { }; Maps use new Map().

TL;DR

• A Map stores key-value pairs.
• set adds, get reads, has checks, delete removes.
• Keys can be any type.
• Maps keep insertion order.