js中深拷贝与浅拷贝的详细介绍（代码分析）

let obj = {
 name: 'leeper',
 age: 20,
 friend: {
 name: 'lee',
 age: 19
 }
};
let copyObj = JSON.parse(JSON.stringify(obj));
obj.name = 'Sandman';
obj.friend.name = 'Jerry';
console.log(obj);
// -> {name: "Sandman", age: 20, friend: {age: 19,name: 'Jerry'}}
console.log(copyObj);
// -> {name: "leeper", age: 20, friend: {age: 19,name: 'lee'}}

// 深拷贝
function deepCopy(obj) {
 if (!obj && typeof obj !== 'object') {
 throw new Error('error arguments');
 }
 // const targetObj = obj.constructor === Array ? [] : {};
 const targetObj = Array.isArray(obj) ? [] : {};
 for (let key in obj) {
 
 //只对对象自有属性进行拷贝
 if (obj.hasOwnProperty(key)) {
 if (obj[key] && typeof obj[key] === 'object') {
 targetObj[key] = deepCopy(obj[key]);
 } else {
 targetObj[key] = obj[key];
 }
 }
 }
 return targetObj;
}