Making Changes To A Copied Array, Updates The Original?

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

Solution 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.

Solution 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 = newArray(users);

clone[0].name = 'Jeff';

console.log(clone[0].name) //jeffconsole.log(users[0].name) //john