JavaScript Maps

A Map stores key value pairs.

Unlike plain objects, keys can be any type.

Think of a locker wall. Each locker key can open one box.

Create a Map

Use new Map().

set and get

set stores a value under a key.

get reads it back.

Any key type

Objects can use numbers as keys only after turning them into strings.

Maps keep the real key type.

has, delete, size

has checks for a key. delete removes a pair. size counts pairs.

Loop

You can loop keys, values, or entries.

Map vs object

Use a plain object for simple record shapes.

Use a Map when keys are weird types or you need frequent add and remove.

Tip: Remember get and set. Those two verbs unlock most Map work.