Q6：实现add(3)(4)和add(3,4) 都输出7，请实现add方法

const add = (...args) => {
  let result = [...args].reduce((res, item) => res + item)
  const next = (..._args) => {
    result = [..._args].reduce((_res, _item) => {
      return _res + _item
    }, result)
    return next
  }
  next.toString = () => result
  return next
}
console.log(add(1)(2)(3, 4)) // 10