Merge object deeply

deepMerge.js

const deepMerge = (target = {}, origin = {}) => {
  const toString = Object.prototype.toString;

  for (let prop in origin) {
    let originProp = origin[prop],
        targetProp = target[prop];

    if (typeof originProp === 'object') {
      if (toString.call(originProp) === '[object Object]') {
        target[prop] = {};
      } else if(toString.call(originProp) === '[object Array]') {
        target[prop] = [];
      }

      deepClone(targetProp, originProp);
    } else {
      targetProp = originProp;
    }
  }

  return target;
};