JavaScript - 复制对象数组并在不修改原始数组的情况下进行更改

时间:2017-08-04 17:46:01

标签: javascript arrays ecmascript-6 immutability

我有一个对象数组。我想深度复制对象数组并对每个对象进行一些更改。我想这样做而不修改原始数组或该数组中的原始对象。

这就是我做的方式。但是,作为JavaScript的新手,我想确保这是一个很好的方法。

有更好的方法吗?

const users = 
[
    {
        id       : 1,    
        name     : 'Jack',
        approved : false
    },
    {
        id       : 2,    
        name     : 'Bill',
        approved : true
    },
    {
        id       : 3,    
        name     : 'Rick',
        approved : false
    },
    {
        id       : 4,    
        name     : 'Rick',
        approved : true
    }
];


const users2 = 
    users
        .map(
            (u) => 
            {
                return Object.assign({}, u);
            }
        )    
        .map(
            (u) => 
            {
                u.approved = true;
                return u;
            }
        );    


console.log('New users2 array of objects:')
console.log(users2);

console.log('This was original users array is untouched:')
console.log(users);

输出:

New users2 array of objects:
[ { id: 1, name: 'Jack', approved: true },
  { id: 2, name: 'Bill', approved: true },
  { id: 3, name: 'Rick', approved: true },
  { id: 4, name: 'Rick', approved: true } ]
This was original users array is untouched:
[ { id: 1, name: 'Jack', approved: false },
  { id: 2, name: 'Bill', approved: true },
  { id: 3, name: 'Rick', approved: false },
  { id: 4, name: 'Rick', approved: true } ]

4 个答案:

答案 0 :(得分:8)

对于单次传递,您也可以将Object.assign与更改的属性一起使用。



const users = [{ id: 1, name: 'Jack', approved: false }, { id: 2, name: 'Bill', approved: true }, { id: 3, name: 'Rick', approved: false }, { id: 4, name: 'Rick', approved: true }];
const users2 = users.map(u => Object.assign({}, u, { approved: true }));

console.log(users2);
console.log(users);

.as-console-wrapper { max-height: 100% !important; top: 0; }




答案 1 :(得分:3)

是的,看起来不错。您还可以在克隆时执行修改,以避免在阵列上映射两次。

const users2 = users.map((u) => {
    const copiedUser = Object.assign({}, u);
    copiedUser.approved = true;
    return copiedUser;
}); 

答案 2 :(得分:1)

有几种方法可以在javascript中复制数组,我相信最常用的是:

  • 切片()
  • Array.from()

slice函数将返回给定数组的一部分(或所有内容)作为新数组,基于开始和结束索引(开始和结束索引是可选的):

const a = [1,2,3,4,5,6,7,8,9]
/*
* Only begin index
*/
const b = a.slice(2)
console.log(b) //Will Print [3,4,5,6,7,8,9]
/*
* Begin index and end index
*/
const c = a.slice(5,8)
console.log(c) //Will Print [6,7,8]
/*
* No indexes provided
*/
const d = a.slice()
console.log(d) //Will print [1,2,3,4,5,6,7,8,9]

Array.from()是一个函数,它将从类似数组或可迭代的参数创建一个新数组。

const a = Array.from('bar');
console.log(a) //Will Print ["b","a","r"]
const b = ["for","bar"];
const c = Array.from(b);
console.log(c) //Will print  ["for","bar"]

More about slice

More about Array.from()

答案 3 :(得分:1)

我更喜欢JSON.stringify和JSON.parse

var users = [ { id: 1, name: 'Jack', approved: false },
{ id: 2, name: 'Bill', approved: true },
{ id: 3, name: 'Rick', approved: false },
{ id: 4, name: 'Rick', approved: true } ];

// user2 will be copy of array users without reference
var users2 = JSON.parse(JSON.stringify(users));