Object.assign() keep all the unchaged values

Question

I'm using Object.assign wrong?

I tought it will replace the values, but actually it overwrites them...

For example the 'PEACH' property will be deleted after being assigned.

Isn't it strange? How would you solve this?

Let's save PEACH

var result = Object.assign({
  'first_level': {
    'second_level': {
      'changeme': 'not changed bruh',
      'PEACH': 'PLEASE SAVE ME!'
    }
  },
  'hehe' : 'I will stay here'
}, {
  'first_level': {
    'second_level': {
      'change': 'Changed B]',
      'addme': 'Extra prop'
    }
  },
  'huh' : 'I want to join the party'
});

document.body.innerHTML = '<pre>'+JSON.stringify(result, null, 2)+'</pre>';

It's just non recursive. If you want a recursive assign, you must code it yourself. — Denys Séguret, Oct 18 '18 at 10:54
it takes the first level of properties and replace it with the values of the second. — Nina Scholz, Oct 18 '18 at 10:54
Why not just read [the docs](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign) before asking? — hindmost, Oct 18 '18 at 10:57

score 1 · Answer 1 · answered Oct 18 '18 at 11:00

1

Object.assign does only a shallow Merge. You can use lodash merge for this it does recursively merge the Objects.

answered Oct 18 '18 at 11:00

Pascal L.

1,261
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score 0 · Accepted Answer · answered Oct 18 '18 at 11:00

While Object.assign assign only the first level, you could iterate the entries of the objects and assign either the value or for object the nested assigned values.

function deeperAssign(a, b) {
    Object
        .entries(b)
        .forEach(([k, v]) => a[k] = v && typeof v === 'object'
            ? deeperAssign(a[k] = a[k] || {}, v)
            : v
        );
    return a;
}

var result = deeperAssign(
        { first_level: { second_level: { changeme: 'not changed bruh', PEACH: 'PLEASE SAVE ME!' } }, hehe: 'I will stay here' },
        { first_level: { second_level: { change: 'Changed B]', addme: 'Extra prop' } }, huh: 'I want to join the party' }
    );

console.log(result);

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

Object.assign() keep all the unchaged values

2 Answers2