更改复制数组，更新原始数组？

Question

I have an array of objects:

 let users = [{name: 'john', address: '10 king street'}, ....];

I copy this array via:

let usersCopy = users.slice(0);

Then if I do

usersCopy[0].name = jeff;

It also updated this on the original users array:

console.log(usersCopy[0].name) //jeff
console.log(users[0].name) //jeff

I'm expecting to see:

console.log(usersCopy[0].name) //jeff
console.log(users[0].name) //john

Answer 1

That's because [].slice() does a shallow copy, meaning you get a new array, but it doesn't clone the objects underneath. Therefore, users[0] === usersCopy[0] , as they are the same reference to the same object.

You will need to replace usersCopy[0] entirely. For example:

usersCopy[0] = {...usersCopy[0], name: 'jeff'}

Which would create a new object with everything from usersCopy[0] shallow-copied into it.

Answer 2

Edit: As noted below this answer is not correct

Here's an alternate way to create a separate array from the original so you can modify the clone

 const users = [{name: 'John', address: '10 king street'}]; const clone = new Array(users); clone[0].name = 'Jeff'; console.log(clone[0].name) //jeff console.log(users[0].name) //john