JS group nested array by date field

Question

I have such an array structure:

[
  {
    group: "perf",
    subgroups: [
      {
        date: "2020-08-20",
        number: 2
      },
      {
        date: "2020-08-21",
        number: 3
      }
    ],
    number: 5
  },
  {
    group: "mobile",
    subgroups: [
      {
        date: "2020-08-20",
        number: 4
      },
      {
        date: "2020-08-21",
        number: 6
      }
    ],
    number: 10
  },
  {
    group: "games",
    subgroups: [
      {
        date: "2020-08-20",
        number: 7
      },
      {
        date: "2020-08-21",
        number: 8
      },
        {
        date: "2020-08-22",
        number: 1
      }
    ],
    number: 16
  },
  {
    group: "levels",
    subgroups: [
      {
        date: "2020-08-09",
        number: 4
      },
      {
        date: "2020-08-20",
        number: 9
      },
      {
        date: "2020-08-21",
        number: 11
      }
    ],
    number: 24
  }
]

I need to create a mapper over this array to receive such output:

total - the overall sum of numbers for the specific date.

[
    {
      date: "2020-08-09",
      total: 4,
      levels: 4
    },
    {
      date: "2020-08-20",
      total: 22,
      perf: 2,
      mobile: 4,
      games: 7,
      levels: 9,
    },
    {
      date: "2020-08-21",
      total: 28,
      perf: 3,
      mobile: 6,
      games: 8,
      levels: 11,
    },
    {
      date: "2020-08-22",
      total: 1,
      games: 1
    }
]

How can this be achieved? I was trying, using reduce but cannot figure out, how to group it by dates.

Here's what I've tried so far: https://jsfiddle.net/wqhj62od/

Or maybe it can be done easily using lodash?

Thank you!

hgb123 · Accepted Answer · 2020-09-10 19:09:16Z

You could do this with plain JS, require some manipulation here

group total value of each type by date
map through the group and calculate the total of all values

const dateValueLookup = arr.reduce((acc, el) => {
  el.subgroups.forEach((subgroup) => {
    if (!acc[subgroup.date]) {
      acc[subgroup.date] = {}
    }
    if (!acc[subgroup.date][el.group]) {
      acc[subgroup.date][el.group] = 0
    }
    acc[subgroup.date][el.group] += subgroup.number
  })
  return acc
}, {})

const res = Object.entries(dateValueLookup)
  .sort(([keyA], [keyB]) => keyA.localeCompare(keyB))
  .map(([date, values]) => ({
    date,
    total: Object.values(values).reduce((sum, value) => sum + value, 0),
    ...values,
  }))

const arr = [
  {
    group: "perf",
    subgroups: [
      {
        date: "2020-08-20",
        number: 2,
      },
      {
        date: "2020-08-21",
        number: 3,
      },
    ],
    number: 5,
  },
  {
    group: "mobile",
    subgroups: [
      {
        date: "2020-08-20",
        number: 4,
      },
      {
        date: "2020-08-21",
        number: 6,
      },
    ],
    number: 10,
  },
  {
    group: "games",
    subgroups: [
      {
        date: "2020-08-20",
        number: 7,
      },
      {
        date: "2020-08-21",
        number: 8,
      },
      {
        date: "2020-08-22",
        number: 1,
      },
    ],
    number: 16,
  },
  {
    group: "levels",
    subgroups: [
      {
        date: "2020-08-09",
        number: 4,
      },
      {
        date: "2020-08-20",
        number: 9,
      },
      {
        date: "2020-08-21",
        number: 11,
      },
    ],
    number: 24,
  },
]

const dateValueLookup = arr.reduce((acc, el) => {
  el.subgroups.forEach((subgroup) => {
    if (!acc[subgroup.date]) {
      acc[subgroup.date] = {}
    }
    if (!acc[subgroup.date][el.group]) {
      acc[subgroup.date][el.group] = 0
    }
    acc[subgroup.date][el.group] += subgroup.number
  })
  return acc
}, {})

const res = Object.entries(dateValueLookup)
  .sort(([keyA], [keyB]) => keyA.localeCompare(keyB))
  .map(([date, values]) => ({
    date,
    total: Object.values(values).reduce((sum, value) => sum + value, 0),
    ...values,
  }))

console.log(res)

trincot · Accepted Answer · 2020-09-10 19:25:25Z

You could create a Map keyed by date, with the final objects as values. Then iterate the data and update those objects. Finally extract the values from the Map and sort them:

function ungroup(data) {
    let map = new Map(data.flatMap(({subgroups}) => 
        subgroups.map(({date}) => [date, { date, total: 0 }])
    ));
    for (let {group, subgroups} of data) {
        for (let {date, number} of subgroups) {
            let obj = map.get(date);
            obj.total += obj[group] = number;
        }
    }
    return Array.from(map.values()).sort((a, b) => a.date.localeCompare(b.date));
}

let data = [{group: "perf",subgroups: [{date: "2020-08-20",number: 2},{date: "2020-08-21",number: 3}],number: 5},{group: "mobile",subgroups: [{date: "2020-08-20",number: 4},{date: "2020-08-21",number: 6}],number: 10},{group: "games",subgroups: [{date: "2020-08-20",number: 7},{date: "2020-08-21",number: 8},{date: "2020-08-22",number: 1}],number: 16},{group: "levels",subgroups: [{date: "2020-08-09",number: 4},{date: "2020-08-20",number: 9},{date: "2020-08-21",number: 11}],number: 24}];
let result = ungroup(data);
console.log(result);

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