Updating copied object also updates the parent object

Question

I have got an object of defaults, then some values which will over-ride the defaults. However when i use Object.assign to create a new object, and update this, the defaults also get changed.

let defaults = { test: 'hello world' };
let values = { test: 'beep' };
let merged = Object.assign(defaults, values);

merged.test = 'updated'

// defaults: { test: 'updated' }

Defaults should remain the same and only merged should get updated. I was under the impression that Object.assign copies the object, not references it.

Use spread operator to merge ``let merged = {...defaults, ...values}`` — Ravi Kukreja, Jul 22 '20 at 08:46

score 4 · Accepted Answer · answered Jul 22 '20 at 08:46

4

Do it in following way.

let defaults = { test: 'hello world' };
let values = { test: 'beep' };
let merged = Object.assign({}, defaults, values);

merged.test = 'updated';

console.log(defaults)

answered Jul 22 '20 at 08:46

Sandip Nirmal

2,283
21
24

score 1 · Answer 2 · answered Jul 22 '20 at 08:47

1

You can try: let merged = Object.assign({}, defaults, values);

answered Jul 22 '20 at 08:47

Max Peng

2,879
1
26
43

score 0 · Answer 3 · answered Jul 22 '20 at 08:48

Ciao, try to clone deppe your merged array. Here working example using lodash:

let defaults = { test: 'hello world' };
let values = { test: 'beep' };
let merged = Object.assign(defaults, values);
let merged_deepclone = _.cloneDeep(merged);

merged_deepclone.test = 'updated';

console.log(defaults);
console.log(merged_deepclone);

<script src="https://cdn.jsdelivr.net/npm/lodash@4.17.10/lodash.min.js"></script>

Updating copied object also updates the parent object

3 Answers3