Sized Map

ES6 Map with a configurable max size.

Features

• Written using TypeScript (and thus fully typed, supporting TypeScript and JavaScript).
• Lightweight.
• Same interface as ECMAScript's Map, you can substitute it almost seamlessly (only need to set its maxSize in the constructor).
• Supports ESM and CJS.

Installation

# npm
npm i sized-map

# yarn
yarn add sized-map

Usage

The following examples use TypeScript and ESM import ... from ..., but it works the same with JavaScript and/or CJS.

Create a new instance:

import SizedMap from 'sized-map'
const map = new Map<string, number>(3)

Add keys and values:

map.set('a', 1)
map.set('b', 2)
map.set('c', 3)
console.log(map)
// SizedMap(3) [Map] { 'a' => 1, 'b' => 2, 'c' => 3 }

When you try to set a new key and it has reached its max length, it will remove the oldest key.

map.set('d', 4)
console.log(map)
// SizedMap(3) [Map] { 'b' => 2, 'c' => 3, 'd' => 4 }

You can also change the max size of an already created SizedMap:

map.maxSize = 1
console.log(map)
// SizedMap(1) [Map] { 'd' => 4 }

If the newSize is smaller than its originalSize, it will remove originalSize - newSize elements, keeping the most recent ones.

Notes

Setting an already set key will be treated as a new key. In the following example, a isn't removed because it was re-set after b.

const map = new Map<string, number>(2)
map.set('a', 1)
map.set('b', 2)
map.set('a', 3)
map.set('c', 4)
map.set('d', 5)
// SizedMap(3) [Map] { 'a' => 3, 'c' => 4, 'd' => 5 }