"FUNctional" 😜 Map 🗺 to object 🔑

map-to-object.js

const obj = { a: 1, c: 3, b: 2 }

// Map from object.
const myMap = new Map(Object.entries(obj))

// Map to Object. 
// NOTE: Keys will be cast to strings by `.toString`, so any "complex" key like for example `[1, 2]` will become `1,2`
const newObj = [...myMap.entries()]
  .reduce((acc, [key, value]) => (Object.assign(acc, { [key]: value })), {})

const newObjWithObjSpreadSyntax = [...myMap.entries()]
  .reduce((acc, [key, value]) => ({...acc, [key]: value }), {})

/* --------- */

// As a fn (breakdown).
/*
 * Creates a copy of the `acc` object adding a new property determined by `key` and `value`.
 * NOTE: Keys will be cast to strings by `.toString`, 
 * so any "complex" key like for example `[1, 2]` will become `1,2`
 */
const keyValuePairToObjReducer = (acc, [key, value]) => ({...acc, [key]: value })

/*
 * Read as: Given a map => Get it's entries
 *   -> Spread them into an array of [key, pair] 
 *   -> Reduce the [key, pair] collection calling `keyValuePairToObjReducer`
 */
const mapToObject = (map) => [...map.entries()].reduce(keyValuePairToObjReducer, {})

const myObj = mapToObject(myMap)

small variation : const mapToObject = (map) => Object.assign({},...[...map].map(([k,v])=>({[k]:v})))