How do I arrange a javascript array of objects from one format to another

Question

I feel like its a very simple answer but im having trouble figuring it out.

I want to turn this array of objects:

[{
    client: 'lalala@email.com',
    amount: 0,
    date: '2018-12'
},
{
    client: 'lalala@email.com',
    amount: '30',
    date: '2018-11'
}, {
    client: 'lalala@email.com',
    amount: '5',
    date: '2018-10'
}]

Into this:

[{
    client: 'lalala@email.com',
    '2018-12': 0,
    '2018-11': '30',
    '2018-10': '5'
}]

I've been trying with reduce() function but not getting anywhere close.

I appreciate you taking the time.

Can your array contain objects with various `client` email values or is it always the same one? — nem035, Dec 30 '18 at 02:07
Then checkout [the answer by ic3b3rg](https://stackoverflow.com/a/53974785/3928341) — nem035, Dec 30 '18 at 02:09
Is it possible to have duplicate dates with different amounts? — Anatoli Klamer, Dec 30 '18 at 02:39

score 4 · Accepted Answer · answered Dec 30 '18 at 02:07

4

A reduce is the correct approach - here's how to do it:

const data = [{
    client: 'lalala@email.com',
    amount: 0,
    date: '2018-12'
},
{
    client: 'lalala@email.com',
    amount: '30',
    date: '2018-11'
}, {
    client: 'lalala@email.com',
    amount: '5',
    date: '2018-10'
}]

const result = data.reduce((memo, {client, date, amount}) => {
  memo.client = client;
  memo[date] = amount;
  return memo;
}, {});

console.log(result)

answered Dec 30 '18 at 02:07

ic3b3rg

14,629
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Do you mind explaining this code `data.reduce((memo, {client, date, amount})` – brk Dec 30 '18 at 04:34
`memo` is the accumulator that is either the initialized value (`{}` in this case) or the returned value from the last iteration. `{client, date, amount}` are decomposed properties of each object in the iteration. make sense? – ic3b3rg Dec 30 '18 at 04:37

connexo · Answer 2 · 2018-12-30T02:20:51.657

Using Array.prototype.reduce this would work:

const a = [{
    client: 'lalala@email.com',
    amount: 0,
    date: '2018-12'
}, {
    client: 'lalala@email.com',
    amount: '30',
    date: '2018-11'
}, {
    client: 'lalala@email.com',
    amount: '5',
    date: '2018-10'
}]

const b = a.reduce((acc, {date, amount}) => {
  return { ...acc, [date]: amount }
}, { client: a[0].client })

console.log([b])

score 1 · Answer 3 · answered Dec 30 '18 at 02:12

Since the client will always be the same you can put Object.assign to good work in reduce():

const data = [{client: 'lalala@email.com',amount: 0,date: '2018-12'},{client: 'lalala@email.com',amount: '30',date: '2018-11'}, {client: 'lalala@email.com',amount: '5',date: '2018-10'}]

const result = data.reduce((obj, {client, date, amount}) => 
    Object.assign(obj, {client, [date]:amount}), {});

console.log([result])

How do I arrange a javascript array of objects from one format to another

3 Answers3