手写一个深拷贝

不可能拷贝 proto

const cache = new Map()//缓存已拷贝部分
function clone(object){
  if(cache.get(object)){//假如已缓存，直接返回
      return cache.get(object)
  }
  let result
  if(! (object instanceof Object) ){//基础类型直接返回
      return object
  }else if(object instanceof Array){
      result = []
  }else if(object instanceof Function){
     result = function(){return object.apply(this,arguments)}
  }else if(object instanceof Date){
      result = new Date(object-0)
  }
  else if(object instanceof RegExp){
      result = new RegExp(a)
  }else{
      result = {}
  }
  cache.set(object,result)//插入缓存
  for(let key in object){
      if(object.hasOwnProperty(key)){//非继承属性
          result[key] = clone(object[key])
      }
  }
  return result
}