µmap 🗺

The smallest, yet handy, Map and WeakMap utility ever.

import umap from 'umap';
// const umap = require('umap');

const map = umap(new Map);
console.assert(
  (map.get(1) || map.set(1, Math.random())) ===
  (map.get(1) || map.set(1, Math.random())),
  'a very common pattern I have with Map instances'
);

const weakMap = umap(new WeakMap);
console.assert(
  (weakMap.get(map) || weakMap.set(map, Math.random())) ===
  (weakMap.get(map) || weakMap.set(map, Math.random())),
  'which I use even more with WeakMap instances'
);

🤔 Reason

I am super tired of creating workarounds for the fact map.set(key, value) doesn't return value but the map itself, and so does the WeakMap.

This module will help, at least me, dropping all one-off helpers, here and there, to always do the same thing:

// before 😢
const cache = new WeakMap;
const setThing = (key, value) => {
  cache.set(key, value);
  return value;
};
const thing = cache.get(key) || setThing(key, value);

// with umap 🎉
const cache = umap(new WeakMap);
const thing = cache.get(key) || cache.set(key, value);

🌈 It's Done!

This module is meant to solve one pattern only, and it does exactly that, so that if you store falsy values in Maps or WeakMaps, it is not a concern of this module.