Convert ES6 `Map`s to a standard JSON object without effing Babel.

map-to-json.js

/**
 * Convert a `Map` to a standard
 * JS object recursively.
 * 
 * @param {Map} map to convert.
 * @returns {Object} converted object.
 */
function map_to_object(map) {
    const out = Object.create(null)
    map.forEach((value, key) => {
      if (value instanceof Map) {
        out[key] = map_to_object(value)
      }
      else {
        out[key] = value
      }
    })
    return out
  }