Javascript extend sub object

Question

I'm trying to add new properties to obj sub in object1. However its getting overwritten

const object1 = {
  a: 1,
  b: 2,
  c: 3,
  sub: {
    e: 1,
    f: 2
  }
};

const object2 = Object.assign({
  j: 4,
  m: 5
}, object1.sub);

console.log(object2);

How do you mean "getting overwritten"? I would expect this to log { e:1, f:2, j:4, m:5 }? The way you have it written, you are taking object { j: 4, m: 5 } and adding the properties from object1.sub to it, then assigning that to object2. — Alexander Nied
– Alexander Nied, Commented Apr 3, 2018 at 20:20

Nina Scholz · Accepted Answer · 2018-04-03 20:20:33Z

6

You could switch the parameters for Object.assign, because the target is coming first.

const object = { a: 1, b: 2, c: 3, sub: { e: 1, f: 2 } };

Object.assign(object.sub, { j: 4, m: 5 });

console.log(object);

answered Apr 3, 2018 at 20:20

Nina Scholz

388k26 gold badges367 silver badges417 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

lekterable · Accepted Answer · 2018-04-03 20:47:17Z

1

With ES6 syntax:

const object1 = { a: 1, b: 2, c: 3, sub: { e: 1, f: 2 } };
const object2 = {...object1, sub: {...object1.sub, j: 4, m: 5}}
console.log(object2)

edited Apr 3, 2018 at 20:47

answered Apr 3, 2018 at 20:26

lekterable

1,0772 gold badges10 silver badges18 bronze badges

2 Comments

Abslen Char Over a year ago

did you test it ?

lekterable Over a year ago

oops2, got it now

Collectives™ on Stack Overflow

Javascript extend sub object

2 Answers 2

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related