来源 | https://www.fly63.com/

浅拷贝与深拷贝

1、JSON.parse(JSON.stringify(obj))

let a = {a:1,b:2}let b = JSON.parse(JSON.stringify(a))a.a = 11console.log(a)//{a:1,b:2}console.log(b)//{a:11,b:2}

1.1 JSON.parse(JSON.stringify(obj))深浅拷贝的缺陷

let a = {    name: 'Jack',    age: 18,    hobbit: ['sing', {type: 'sports', value: 'run'}],    score: {        math: 'A',    },    run: function() {},    walk: undefined,    fly: NaN,    cy: null,    date: new Date()}let b = JSON.parse(JSON.stringify(a))console.log(b)// {//     age: 18,//     cy: null,//     date: "2022-05-15T08:04:06.808Z"//     fly: null,//     hobbit: (3) ["dance", "sing", {…}],//     name: "Jack",//     score: {math: "A"},// }

取不到值为 undefined 的 key；如果对象里有函数，函数无法被拷贝下来；无法拷贝copyObj对象原型链上的属性和方法；对象转变为 date 字符串。

2、普通递归函数实现深拷贝

function deepClone(source) {  if (typeof source !== 'object' || source == null) {    return source;  }  const target = Array.isArray(source) ? [] : {};  for (const key in source) {    if (Object.prototype.hasOwnProperty.call(source, key)) {      if (typeof source[key] === 'object' && source[key] !== null) {        target[key] = deepClone(source[key]);      } else {        target[key] = source[key];      }    }  }  return target;}

2.1、解决循环引用和symblo类型

function cloneDeep(source, hash = new WeakMap()) {  if (typeof source !== 'object' || source === null) {    return source;  }  if (hash.has(source)) {    return hash.get(source);  }  const target = Array.isArray(source) ? [] : {};  Reflect.ownKeys(source).forEach(key => {    const val = source[key];    if (typeof val === 'object' && val != null) {      target[key] = cloneDeep(val, hash);    } else {      target[key] = val;    }  })  return target;}

3、兼容多种数据类型

const deepClone = (source, cache) => {  if(!cache){    cache = new Map()   }  if(source instanceof Object) { // 不考虑跨 iframe    if(cache.get(source)) { return cache.get(source) }    let result     if(source instanceof Function) {      if(source.prototype) { // 有 prototype 就是普通函数        result = function(){ return source.apply(this, arguments) }      } else {        result = (...args) => { return source.call(undefined, ...args) }      }    } else if(source instanceof Array) {      result = []    } else if(source instanceof Date) {      result = new Date(source - 0)    } else if(source instanceof RegExp) {      result = new RegExp(source.source, source.flags)    } else {      result = {}    }    cache.set(source, result)    for(let key in source) {       if(source.hasOwnProperty(key)){        result[key] = deepClone(source[key], cache)       }    }    return result  } else {    return source  }}

4、jquery.extend()方法

可以使用$.extend进行深拷贝$.extend(deepCopy, target, object1, [objectN])//第一个参数为true,就是深拷贝
let a = {    a: 1,    b: { d:8},    c: [1, 2, 3]};let b = $.extend(true, {}, a);console.log(a.b.d === b.b.d); // false

4.1、 jQuery.extend 源码

jQuery.extend = jQuery.fn.extend = function() {  var options,    name,    src,    copy,    copyIsArray,    clone,    target = arguments[0] || {},    i = 1,    length = arguments.length,    deep = false;
  // Handle a deep copy situation  if (typeof target === "boolean") {    deep = target;
    // Skip the boolean and the target    target = arguments[i] || {};    i++;  }
  // Handle case when target is a string or something (possible in deep copy)  if (typeof target !== "object" && !jQuery.isFunction(target)) {    target = {};  }

总结

以上就是我今天跟你分享的4个关于JavaScript深拷贝的方法，希望对你有帮助。

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