Array to object with based on given key

Question

I have an array declared which uses the Object.assign:

var obj = [{
  id: 1,
  value: 'abc'
}, {
  id: 2,
  value: 'xyz'
}];

console.log(Object.assign({}, obj));

it's getting transformed as,

{ 
    '0': { id: 1, value: 'abc' }, 
    '1': { id: 2, value: 'xyz' } 
}

However I need to have this as, (here the 1 and 2 represents the id attribute of my object)

{
        '1': {id: 1, value: 'abc'},
        '2': {id: 2, value: 'xyz'}
}

I've tried few, but had no luck, Can someone shed some light?

Why do you need it to be one and not zero? The first key in an ordinal array is typically going to be 0. — Adam Carr
– Adam Carr, Commented Apr 24, 2018 at 14:30

Nina Scholz · Accepted Answer · 2018-04-24 14:37:25Z

6

You could map the objects in an object with the wanted key and assign it to a single object.

var objects = [{ id: 1, value: 'abc' }, { id: 2, value: 'xyz' }],
    result = Object.assign(...objects.map(o => ({ [o.id]: o })));
    
console.log(result);

edited Apr 24, 2018 at 14:37

answered Apr 24, 2018 at 14:30

Nina Scholz

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Comments

James Risner · Accepted Answer · 2023-03-30 16:35:35Z

4

You can use reduce() method with Object.assign.

var obj = [{id: 1, value: 'abc'}, {id: 2, value: 'xyz'}];
var result = obj.reduce((r, e) => Object.assign(r, {[e.id]: e}), {});
console.log(result)

Note that we are passing a reference of each object in a array and not creating new objects, but you can change that with object assign on e or you can use spread syntax like so:

Object.assign(r, {[e.id]: {...e}})

edited Mar 30, 2023 at 16:35

James Risner

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answered Apr 24, 2018 at 14:29

Nenad Vracar

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Comments

31piy · Accepted Answer · 2018-04-24 14:29:53Z

3

You can directly use Array#reduce to do that, and there is no need for Object.assign here:

var obj = [{id: 1, value: 'abc'}, {id: 2, value: 'xyz'}];

let result = obj.reduce((acc, item) => {
  acc[item.id] = item;
  return acc;
}, {});

console.log(result);

answered Apr 24, 2018 at 14:29

31piy

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Eddie · Accepted Answer · 2018-04-24 14:30:24Z

3

If you want to use .id to be the key, you can use reduce and use Object.assign

let obj = [{id: 1,value: 'abc'}, {id: 2,value: 'xyz'}];

let result = obj.reduce((c, v) => Object.assign(c, {[v.id]: v}), {});

console.log(result);

answered Apr 24, 2018 at 14:30

Eddie

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