code: function each (obj, iterate, context) {
    if (obj) {
      context = context || this
      if (isArray(obj)) {
        return arrayEach(obj, iterate, context)
      }
      return objectEach(obj, iterate, context)
    }
    return obj
  }
docs: 迭代器
  
  @param {Object} obj 对象/数组
  @param {Function} iterate(item, index, obj) 回调
  @param {Object} context 上下文
  @return {Object}