js 深浅拷贝

浅拷贝

object.assign

扩展运算符

concat (数组)

sblice (数组)

深拷贝

JSON.stringfy()

手写递归实现

let obj1 = {
  a: {
    b: 1,
  },
};

function deepClone(obj) {
  let cloneObj = Array.isArray(obj) ? [] : {};

  for (let key in obj) {
    //遍历

    if (typeof obj[key] === "object") {
      cloneObj[key] = deepClone(obj[key]); //是对象就再次调用该函数递归
    } else {
      cloneObj[key] = obj[key]; //基本类型的话直接复制值
    }
  }

  return cloneObj;
}

let obj2 = deepClone(obj1);

obj1.a.b = 2;

console.log(obj2); //  {a:{b:1}}

改进后递归实现

const isComplexDataType = (obj) =>
  (typeof obj === "object" || typeof obj === "function") && obj !== null;

const deepClone = function (obj, hash = new WeakMap()) {
  if (obj.constructor === Date) return new Date(obj); // 日期对象直接返回一个新的日期对象

  if (obj.constructor === RegExp) return new RegExp(obj); //正则对象直接返回一个新的正则对象

  //如果循环引用了就用 weakMap 来解决

  if (hash.has(obj)) return hash.get(obj);

  let allDesc = Object.getOwnPropertyDescriptors(obj);

  //遍历传入参数所有键的特性

  let cloneObj = Object.create(Object.getPrototypeOf(obj), allDesc);

  //继承原型链

  hash.set(obj, cloneObj);

  for (let key of Reflect.ownKeys(obj)) {
    cloneObj[key] =
      isComplexDataType(obj[key]) && typeof obj[key] !== "function"
        ? deepClone(obj[key], hash)
        : obj[key];
  }

  return cloneObj;
};

// 下面是验证代码

let obj = {
  num: 0,

  str: "",

  boolean: true,

  unf: undefined,

  nul: null,

  obj: { name: "我是一个对象", id: 1 },

  arr: [0, 1, 2],

  func: function () {
    console.log("我是一个函数");
  },

  date: new Date(0),

  reg: new RegExp("/我是一个正则/ig"),

  [Symbol("1")]: 1,
};

Object.defineProperty(obj, "innumerable", {
  enumerable: false,
  value: "不可枚举属性",
});

obj = Object.create(obj, Object.getOwnPropertyDescriptors(obj));

obj.loop = obj; // 设置loop成循环引用的属性

let cloneObj = deepClone(obj);

cloneObj.arr.push(4);

console.log("obj", obj);

console.log("cloneObj", cloneObj);