實(shí)現(xiàn)深拷貝的多種方式

// 只復(fù)制第一層的淺拷貝function simpleCopy(obj1) {   var obj2 = Array.isArray(obj1) ? [] : {};   for (let i in obj1) {   obj2[i] = obj1[i];  }   return obj2;}var obj1 = {   a: 1,   b: 2,   c: {   d: 3  }}var obj2 = simpleCopy(obj1);obj2.a = 3;obj2.c.d = 4;alert(obj1.a); // 1alert(obj2.a); // 3alert(obj1.c.d); // 4alert(obj2.c.d); // 4

 var obj1 = {    a: 1,    b: 2,    c: 3}var obj2 = Object.assign({}, obj1);obj2.b = 5;console.log(obj1.b); // 2console.log(obj2.b); // 5 var obj1 = {    a: 1,    b: 2,    c: ['a','b','c']}var obj2 = Object.assign({}, obj1);obj2.c[1] = 5;console.log(obj1.c); // ["a", 5, "c"]console.log(obj2.c); // ["a", 5, "c"]

// 對(duì)只有一級(jí)屬性值的數(shù)組對(duì)象使用slicevar a = [1,2,3,4];var b = a.slice();b[0] = 2;alert(a); // 1,2,3,4alert(b); // 2,2,3,4// 對(duì)有多層屬性的數(shù)組對(duì)象使用slicevar a = [1,[1,2],3,4];var b = a.slice();b[1][0] = 2;alert(a); // 1,2,2,3,4alert(b); // 1,2,2,3,4

 var a=[1,2,[3,4]] var c=[]; var b=c.concat(a); b[0]=5; b[2][0]=6; console.log(b[0]);//5 console.log(a[0])//1 console.log(b[2][0]);//6 console.log(a[2][0])//6

 var a=[1,2,[3,4]] var b=[...a]; b[0]=5; b[2][0]=6 console.log(b[0]);//5 console.log(a[0])//1 console.log(b[2][0]);//6 console.log(a[2][0])//6

function deepCopy(obj) {  var copy = Object.create(Object.getPrototypeOf(obj));  var propNames = Object.getOwnPropertyNames(obj);
  propNames.forEach(function(name) {    var desc = Object.getOwnPropertyDescriptor(obj, name);    Object.defineProperty(copy, name, desc);  });
  return copy;}
var obj1 = { a: 1, b: {bc: 50, dc: 100, be: {bea: 1}} };var obj2 = deepCopy(obj1);obj2.a = 20;obj2.b.bc = 60;console.log(obj1.a)//1console.log(obj2.a)//20console.log(obj1.b.bc)//60console.log(obj2.b.bc)//60

function deepCopy(obj1){    let _obj = JSON.stringify(obj1);    let obj2 = JSON.parse(_obj);    return obj2;}var a = [1, [1, 2], 3, 4];var b = deepCopy(a);b[1][0] = 2;alert(a); // 1,1,2,3,4alert(b); // 2,2,2,3,4

let obj1 = {   fun:function(){      alert(123);   }}let obj2 = JSON.parse(JSON.stringify(obj1));console.log(typeof obj1.fun); // functionconsole.log(typeof obj2.fun); // undefined

/** * 判斷是否是基本數(shù)據(jù)類型 * @param value */function isPrimitive(value){  return (typeof value === 'string' ||  typeof value === 'number' ||  typeof value === 'symbol' ||  typeof value === 'boolean')}
/** * 判斷是否是一個(gè)js對(duì)象 * @param value */function isObject(value){  return Object.prototype.toString.call(value) === "[object Object]"}
/** * 深拷貝一個(gè)值 * @param value */function cloneDeep(value){
  // 記錄被拷貝的值，避免循環(huán)引用的出現(xiàn)  let memo = {};
  function baseClone(value){    let res;    // 如果是基本數(shù)據(jù)類型，則直接返回    if(isPrimitive(value)){      return value;    // 如果是引用數(shù)據(jù)類型，我們淺拷貝一個(gè)新值來(lái)代替原來(lái)的值    }else if(Array.isArray(value)){      res = [...value];    }else if(isObject(value)){      res = {...value};    }
    // 檢測(cè)我們淺拷貝的這個(gè)對(duì)象的屬性值有沒(méi)有是引用數(shù)據(jù)類型。如果是，則遞歸拷貝    Reflect.ownKeys(res).forEach(key=>{      if(typeof res[key] === "object" && res[key]!== null){        //此處我們用memo來(lái)記錄已經(jīng)被拷貝過(guò)的引用地址。以此來(lái)解決循環(huán)引用的問(wèn)題        if(memo[res[key]]){          res[key] = memo[res[key]];        }else{          memo[res[key]] = res[key];          res[key] = baseClone(res[key])        }      }    })    return res;  }
  return baseClone(value)}

import lodash from 'lodash'
var objects = [1,{ 'a': 1 }, { 'b': 2 }];var deep = lodash.cloneDeep(objects);deep[0] = 2;deep[1].a = 2;console.log(objects[0]);//1console.log(deep[0]);//2console.log(objects[1].a);//1console.log(objects[1].a);//2