手写题：深拷贝

JSON.stringify

JSON.parse(JSON.stringify(obj))

遍历实现

// 利用 WeakMap 解决循环引用
let map = new WeakMap()
function deepClone(obj) {
  if (obj instanceof Object) {
    if (map.has(obj)) {
      return map.get(obj)
    }
    let newObj
    if (obj instanceof Array) {
      newObj = []     
    } else if (obj instanceof Function) {
      newObj = function() {
        return obj.apply(this, arguments)
      }
    } else if (obj instanceof RegExp) {
      // 拼接正则
      newobj = new RegExp(obj.source, obj.flags)
    } else if (obj instanceof Date) {
      newobj = new Date(obj)
    } else {
      newObj = {}
    }
    // 克隆一份对象出来
    let desc = Object.getOwnPropertyDescriptors(obj)
    let clone = Object.create(Object.getPrototypeOf(obj), desc)
    map.set(obj, clone)
    for (let key in obj) {
      if (obj.hasOwnProperty(key)) {
        newObj[key] = deepClone(obj[key])
      }
    }
    return newObj
  }
  return obj
}

递归实现

function deepClone(obj, newObj) {
  var newObj = newObj || {};
  for (let key in obj) {
    if (typeof obj[key] == 'object') {
      newObj[key] = (obj[key].constructor === Array) ? [] : {}
      deepClone(obj[key], newObj[key]);
    } else {
      newObj[key] = obj[key]
    }
  }
  return newObj;
};

递归实现（豆包）

function deepCopy(obj) {
    if (typeof obj!== 'object' || obj === null) {
        return obj; 
    }
 
    let copy = Array.isArray(obj)? [] : {};
 
    for (let key in obj) {
        if (obj.hasOwnProperty(key)) {
            copy[key] = deepCopy(obj[key]);
        }
    }
    return copy;
}

扩展阅读

• 深拷贝浅拷贝的区别！如何实现一个深拷贝！