JS convert Array of Objects into JSON GroupBy Format

Question

I'm trying to find a way to convert the following array of objects into JSON

Original Format

const arr = [
  {
    userid: '1000080542',
    photoname: '2c8a4709-ed7e-00a50-0da4ead1de55118-f3-1473281639’,
    datetime: ‘2020-01-24T20:46:05+11:00’
  },
  {
    userid: '1000081532',
    photoname: '73321038-c8bf-57c6e-5d803cd0a920e9a-95-1487447082',
    datetime: ‘2020-01-24T20:46:05+11:00’
  },
  {
    userid: '1000081532',
    photoname: '5c00bc65-db1b-7a394-dd65b462b9e75e2-c5-1487447019',
    datetime: ‘2020-01-24T20:46:05+11:00’
  },
  {
    userid: '1000081532',
    photoname: '986ee1e2-2f8e-bf070-0d70d2e67537835-e2-1473821119',
    datetime: ‘2020-01-24T20:46:05+11:00’
  },
  {
    userid: '1000081532',
    photoname: '09f7cde6-68c8-f462d-c01f7713a2c747f-eb-1474294185',
    datetime: ‘2020-01-24T20:46:05+11:00’
  }
]

Converted Format

{
            1000080542: {
                '2c8a4709-ed7e-00a50-0da4ead1de55118-f3-1473281639': '2020-01-24T20:46:05+11:00',
                '73321038-c8bf-57c6e-5d803cd0a920e9a-95-1487447082': '2020-01-24T20:46:05+11:00'
            },
            1000081532: {
                '5c00bc65-db1b-7a394-dd65b462b9e75e2-c5-1487447019'': '2020-01-24T20:46:05+11:00',
                '986ee1e2-2f8e-bf070-0d70d2e67537835-e2-1473821119': '2020-01-24T20:46:05+11:00',
                '09f7cde6-68c8-f462d-c01f7713a2c747f-eb-1474294185': '2020-01-24T20:46:05+11:00'
            }
        }

I've been trying along these lines but I'm a big off

obj = arr.reduce((h, y) => {
  Object.keys(y).forEach(k => {
    if (!h[k]) {
      h[k] = []
      h[k].push(y[k])
    } else if (!h[k].includes(y[k])) h[k].push(y[k])
  })
  return h
}, {})
console.log(obj)

thanks

It's unclear why you need Object.keys(y) when you know your top level key is the userid, and you know what the other keys are also — Taplar
– Taplar, Commented Dec 31, 2020 at 0:10

Taplar · Accepted Answer · 2020-12-31 00:16:39Z

const arr = [
  {
    userid: '1000080542',
    photoname: '2c8a4709-ed7e-00a50-0da4ead1de55118-f3-1473281639',
    datetime: '2020-01-24T20:46:05+11:00'
  },
  {
    userid: '1000081532',
    photoname: '73321038-c8bf-57c6e-5d803cd0a920e9a-95-1487447082',
    datetime: '2020-01-24T20:46:05+11:00'
  },
  {
    userid: '1000081532',
    photoname: '5c00bc65-db1b-7a394-dd65b462b9e75e2-c5-1487447019',
    datetime: '2020-01-24T20:46:05+11:00'
  },
  {
    userid: '1000081532',
    photoname: '986ee1e2-2f8e-bf070-0d70d2e67537835-e2-1473821119',
    datetime: '2020-01-24T20:46:05+11:00'
  },
  {
    userid: '1000081532',
    photoname: '09f7cde6-68c8-f462d-c01f7713a2c747f-eb-1474294185',
    datetime: '2020-01-24T20:46:05+11:00'
  }
];

console.log(
  arr.reduce((accumulator, element) => {
    if (!accumulator[element.userid]) accumulator[element.userid] = {};
    
    accumulator[element.userid][element.photoname] = element.datetime;
    
    return accumulator;
  }, {})
);

If I understand your output example correctly, you're wanting to make the top level keys be the userids, and the contents be key value pairs of the photonames to the date times.

So you just need to put the userid in the output object as the key with a sub object as the value, and then put the photonames and datetimes in the sub object.

Unmitigated · Accepted Answer · 2020-12-31 00:19:17Z

You can use reduce with an object to store the values for each id.

const arr = [
  {
    userid: '1000080542',
    photoname: '2c8a4709-ed7e-00a50-0da4ead1de55118-f3-1473281639',
    datetime: '2020-01-24T20:46:05+11:00'
  },
  {
    userid: '1000081532',
    photoname: '73321038-c8bf-57c6e-5d803cd0a920e9a-95-1487447082',
    datetime: '2020-01-24T20:46:05+11:00'
  },
  {
    userid: '1000081532',
    photoname: '5c00bc65-db1b-7a394-dd65b462b9e75e2-c5-1487447019',
    datetime: '2020-01-24T20:46:05+11:00'
  },
  {
    userid: '1000081532',
    photoname: '986ee1e2-2f8e-bf070-0d70d2e67537835-e2-1473821119',
    datetime: '2020-01-24T20:46:05+11:00'
  },
  {
    userid: '1000081532',
    photoname: '09f7cde6-68c8-f462d-c01f7713a2c747f-eb-1474294185',
    datetime: '2020-01-24T20:46:05+11:00'
  }
];
const res = arr.reduce((acc,{userid,photoname,datetime})=>{
  (acc[userid] = acc[userid] || {})[photoname] = datetime;
  return acc;
}, {});
console.log(res);

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