Immutable set like lodash.set but immutable with minimal updates

immutable-set.js

/**
 * Immutable set like lodash.set but immutable with minimal updates
 * @param {Object} o
 * @param {String} path e.g. 'a.b.c'
 * @param {*} val target value
 *
 * @example var o = {a: {b: 1}}, o_ = set(o, 'a.c', 2) // o_ ==== {a: {b: 1, c: 2}}; o is untouched
 *
 * @returns {Object}
 */
export default function set(o, path, val) {
  const keys = path.split('.');
  let isPathComplete = true;
  const root = { ...o };

  const deepestObject = keys.slice(0, keys.length - 1).reduce((o_, key) => {
    if (!o_[key] || o_[key].toString() !== '[object Object]') isPathComplete = false;
    if (!isPathComplete) return o_;
    const o__ = { ...o_[key] };
    Object.assign(o_, { [key]: o__ });
    return o__;
  }, root);

  if (!isPathComplete) {
    console.warn(new Error(`tried to set through incomplete key path "${ path }"`));
    return o;
  }
  deepestObject[keys[keys.length - 1]] = val;
  return root;
}

Пересоздаёт объекты только по пути (path)