How To Group And Sort Object Array?

I've got an object array which I have to group and sort: [ { id: 123, group: 'abc', metadata: { name: 'tom' }, date: ISODate('2019-07-08T20:33:40.475Z')

Solution 1:

Use reduce to group the values, and sort to sort them, using map as well due to the nested array structure.

const arr = [{id:123,group:'abc',metadata:{name:'tom'},date:"2019-07-08T20:33:40.475Z"},{id:456,group:'def',metadata:{name:'bob'},date:"2019-07-08T20:33:40.475Z"},{id:789,group:'def',metadata:{name:'bob'},date:"2019-07-10T20:33:40.475Z"},{id:234,group:'ghi',metadata:{name:'frank'},date:"2019-07-10T20:33:40.475Z"},{id:567,group:'abc',metadata:{name:'tom'},date:"2019-07-10T20:33:40.475Z"}];
const res = Object.values(arr.reduce((a, { group, ...r }) => {
  (a[group] = a[group] || []).push({ group, ...r });
  return a;
}, {})).map(e => e.sort(({ date: a }, { date: b }) =>newDate(a) - newDate(b)));

console.log(res);

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

_{(I've taken out the ISODate function and just kept the string date to make the snippet executable.)}

Solution 2:

I would suggest to use lodash.

var ISODate = function(str) { return str };

var data = [
  {
    id: 123,
    group: 'abc',
    metadata: {
      name: 'tom'
    },
    date: ISODate("2019-07-08T20:33:40.475Z")
  },
  {
    id: 456,
    group: 'def',
    metadata: {
      name: 'bob'
    },
    date: ISODate("2019-07-08T20:33:40.475Z")
  },
  {
    id: 789,
    group: 'def',
    metadata: {
      name: 'bob'
    },
    date: ISODate("2019-07-10T20:33:40.475Z")
  },
  {
    id: 234,
    group: 'ghi',
    metadata: {
      name: 'frank'
    },
    date: ISODate("2019-07-10T20:33:40.475Z")
  },
  {
    id: 567,
    group: 'abc',
    metadata: {
      name: 'tom'
    },
    date: ISODate("2019-07-10T20:33:40.475Z")
  }
]

console.log(
  _.mapValues(
    _.groupBy(data, 'group'),
    function(item) { return _.orderBy(item, ['date'], ['asc']) }
  )
)

https://codepen.io/anon/pen/bPzmOr