Convert ES6 Map to Object Literal

es6-map-to-object-literal.js

let map = new Map();
map.set("a", 1);
map.set("b", 2);
map.set("c", 3);

let obj = Array.from(map).reduce((obj, [key, value]) => (
  Object.assign(obj, { [key]: value }) // Be careful! Maps can have non-String keys; object literals can't.
), {});

console.log(obj); // => { a: 1, b: 2, c: 3 }

If a value in the map can be an array of maps you need:

const toObject = (map = new Map) => {
  if (!(map instanceof Map)) return map
  return Object.fromEntries(Array.from(map.entries(), ([k, v]) => {
    if (v instanceof Array) {
      return [k, v.map(toObject)]
    } else if (v instanceof Map) {
      return [k, toObject(v)]
    } else {
      return [k, v]
    }
  }))
}