对象的深拷贝和浅拷贝总结

发布于 2022-05-26  58 次阅读


1、赋值

修改新对象原来的对象会发生改变(改变存储空间,联动改变)

 let person = {
        name: 'Tom',
        age: 12,
        hobby: ['音乐', '动漫']
    }
    let copyObj = person;
    copyObj.name = '小明';
    copyObj.hobby[0] = '看电视'
    console.log(copyObj, person);
    // { name: '小明', age: 12, hobby: [ '看电视', '动漫' ] } { name: '小明', age: 12, hobby: [ '看电视', '动漫' ] }

2、浅拷贝

浅拷贝 基本类型直接拷贝值(新变原不变),引用类型拷贝内存地址(新变原变)

2.1 使用shallowCopy函数完成浅拷贝

let person = {
        name: 'Tom',
        age: 12,
        hobby: ['音乐', '动漫']
    }
    function shallowCopy(object) {
        var target = {}
        for (const key in object) {
            if (object.hasOwnProperty(key)) {
                target[key] = object[key]
            }
        }
        return target
    }
    let copyObj = shallowCopy(person);
    copyObj.name = '小红';
    copyObj.hobby[0] = '看电影';
    console.log(copyObj, person);
    // { name: '小红', age: 12, hobby: [ '看电影', '动漫' ] } { name: 'Tom', age: 12, hobby: [ '看电影', '动漫' ] }

2.2 使用ES6中的扩展运算符完成浅拷贝

let person = {
        name: 'Tom',
        age: 12,
        hobby: ['音乐', '动漫']
    }
    let copyObj = { ...person };
    copyObj.age = '20';
    copyObj.name = 'Jerry';
    copyObj.hobby[0] = '看文学名著'
    console.log(copyObj, person)
    // { name: 'Jerry', age: '20', hobby: [ '看文学名著', '动漫' ] } { name: 'Tom', age: 12, hobby: [ '看文学名著', '动漫' ] }

3、深拷贝

深拷贝 新变原不变(在堆内存中开辟新的区域,修改不会影响原来的)

3.1 使用deepClone函数实现深拷贝

let person = {
        name: 'Tom',
        age: 12,
        hobby: ['音乐', '动漫']
    }
    function deepClone(object) {
        var cloneObj = Array.isArray(object) ? [] : {};
        if (object === null) return object
        if (object instanceof Date) return new Date(object)
        if (object instanceof RegExp) return new RegExp(object)
        if (typeof object !== 'object') return object
        for (const key in object) {
            if (object.hasOwnProperty(key)) {
                cloneObj[key] = deepClone(object[key])
            }
        }
        return cloneObj
    }

    let copyObj = deepClone(person);
    copyObj.name = 'Marry';
    copyObj.age = 18;
    copyObj.hobby[0] = 'football';
    console.log(copyObj, person);
    // { name: 'Marry', age: 18, hobby: [ 'football', '动漫' ] } { name: 'Tom', age: 12, hobby: [ '音乐', '动漫' ] }

3.2 JSON对象可以使用JSON.parse(JSON.stringify(object)) 的方法实现深拷贝

let obj = {
        key: 1,
        person: {
            name: 'Marry',
            age: 12
        }
    }
    let copyObj = JSON.parse(JSON.stringify(obj));
    copyObj.key = 2;
    copyObj.person.name = 'Bob';
    copyObj.person.age = 13;
    console.log(copyObj,obj)
    // { key: 2, person: { name: 'Bob', age: 13 } } { key: 1, person: { name: 'Marry', age: 12 } }

4、共用方法

4.1 Object.assign()

Object.assign()可实现深拷贝和浅拷贝(当只有一层时为深拷贝,两层及以上为浅拷贝)

let bookInfo = {
        name: '西游记',
        autor: '吴承恩',
        sellstaus: '良好'
    }
    let person = {
        name: 'Tom',
        age: 12,
        hobby: ['音乐', '动漫']
    }
    let copyObj1 = Object.assign({}, bookInfo);
    let copyObj2 = Object.assign({}, person);
    copyObj1.name = '红楼梦',
    copyObj1.autor = '曹雪芹',
    copyObj1.sellstaus = '中等'

    copyObj2.name = '小明',
    copyObj2.age = 22,
    copyObj2.hobby[0] = 'basketball'
    console.log(copyObj1, copyObj2)
    // { name: '红楼梦', autor: '曹雪芹', sellstaus: '中等' } { name: '小明', age: 22, hobby: [ 'basketball', '动漫' ] }

4.2 使用Jquery中的extend方法实现深拷贝和浅拷贝

  • 浅拷贝
    => 语法: $.extend(对象1, 对象2, 对象3, …)
    => 作用: 把从 对象2 开始的所有对象内的数据进行浅拷贝到 对象1 内
    => 实现的是浅拷贝

  • 深拷贝
    => 语法: $.extend(true, 对象1, 对象2, 对象3, …)
    => 作用: 把从 对象2 开始的所有对象内的数据进行深拷贝到 对象1 内
    => 实现的是深拷贝


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