group by array of objects with condition and custom key

Question

I have below array of objects,

[{

    a: 1,
    created_on: '2021-04-23 10:00:01',
}, {
    b: 1,
    created_on: '2021-04-24 09:03:01',
}, {
    b: 1,
    created_on: '2021-04-24 13:03:01',
}]

First, I need to group by with date ignoring times.

So,

{
 "2021-04-23": [{
    a: 1,
    created_on: '2021-04-23 10:00:01',
  }],
....
}

If it were a date like created_on: '2021-04-23', I could use lodash/groupBy.

I still could use it but now it involves some condition to be applied to convert those created_on into date format.

Further, I also need to group by those each grouped by date result as such that their created_on falls within a time interval.

"SALES_SLOTS": [
    {
      "slot": "00:00-04:00"
    },
    {
      "slot": "04:00-08:00"
    }, 
    {
      "slot":"08:00-12:00"
    }, 
    {
      "slot":"12:00-16:00"
    },
    {
      "slot":"16:00-20:00"
    },
    {
      "slot":"20:00-24:00"
    }
  ],

So, if created_on: '2021-04-23 10:00:01', it should come in the group,

{
  "08:00-12:00": [{
     a: 1,
     created_on: '2021-04-23 10:00:01',
  }]
}

So, first results should be grouped by date from created on and then elements in each groups should be further group by defined time slots.

I suppose, if I could use group by condition, I could achieve the desired result.

Please add the code you've tried. There are questions on grouping based on the date like: [How do I group items in an array by date?](https://stackoverflow.com/questions/46802448) — adiga, Apr 26 '21 at 05:12

Som Shekhar Mukherjee · Accepted Answer · 2021-04-27T06:35:22.027

Vanilla JS

Using `Array#reduce` with `Map`.

Grouping by date is fairly simple, you can group the data by created_on.slice(0, 10) using a Map.
Then I've created a helper function getSlot that returns a slot based on the time passed. Now, since your slots are fairly wide, testing just the hour part would be sufficient.
Next, for every group of date, again group it by time using getSlot helper and Map and using Object.fromEntries you can get the desired object.

NOTE: I've used expressions instead of statements inside my code (using commas, defaulted parameters) which is just a preferential choice.

const 
  arr = [{ a: 1, created_on: "2021-04-23 10:00:01" }, { b: 1, created_on: "2021-04-24 09:03:01" }, { b: 1, created_on: "2021-04-24 13:03:01" }],
  
  slots = [{ slot: "00:00-04:00" }, { slot: "04:00-08:00" }, { slot: "08:00-12:00" }, { slot: "12:00-16:00" }, { slot: "16:00-20:00" }, { slot: "20:00-24:00" }],
      
  grpDate = Array.from(
    arr.reduce(
      (m, o, _i, _arr, d = o.created_on.slice(0, 10)) => (
        m.has(d) ? m.get(d).push(o) : m.set(d, [o]), m
      ),
      new Map()
    )
  ),
  
  getSlot = (time) =>
    slots
      .find(({ slot }) => time >= slot.slice(0, 2) && time < slot.slice(6, 8))
      .slot,
      
  grpSlot = grpDate.map(([k, v]) =>
    [k, Object.fromEntries(v.reduce(
      (m, o, _i, _arr, slot = getSlot(o.created_on.slice(11, 13))) => (
        m.has(slot) ? m.get(slot).push(o) : m.set(slot, [o]), m
      ),
      new Map()
    ))]
  );

console.log(Object.fromEntries(grpSlot));

Screenshot of the output

score 1 · Answer 2 · answered Apr 26 '21 at 06:26

This is what I tried using momentjs and lodash.

const bookings = [{
  a: 1,
  created_on: '2021-04-23 10:00:01',
}, {
  b: 1,
  created_on: '2021-04-24 09:03:01',
}, {
  b: 1,
  created_on: '2021-04-24 13:03:01',
}];


const groupedByDate = bookings.reduce((acc, e) => {
  const eDate = moment(e.created_on).format('YYYY-MM-DD');
  if (acc[eDate]) {
    acc[eDate].push(e)
  } else {
    acc[eDate] = [e];
  }
  return acc;
}, { })
const allSlots = ['00:00-04:00', '04:00-08:00', '08:00-12:00', '12:00-16:00','16:00-20:00','20:00-24:00'];
const grupedByDateAndSlots = _.mapValues(groupedByDate, (ele) => {
  return ele.reduce((acc, e) => {
    const createdOnDate = moment(e.created_on).format('YYYY-MM-DD');
    const foundSlot = allSlots.find((slot) => moment(e.created_on).isBetween(moment(`${createdOnDate} ${slot.split('-')[0]}`), moment(`${createdOnDate} ${slot.split('-')[1]}`)))
    if (acc[foundSlot]) {
      acc[foundSlot].push(e)
    } else {
      acc[foundSlot] = [e];
    }
    return acc;
  }, { })
})

console.log(grupedByDateAndSlots)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.21/lodash.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.29.1/moment.min.js"></script>

Got you, I see one problem what if a record is created on exact slots boundary time like `2021-04-23 04:00:00`, in which slot it slot it should be placed? `00:00-04:00` or `04:00-08:00`. I don't think it'll place any of these with existing code. — Ravikumar, Apr 26 '21 at 07:16

Ravikumar · Answer 3 · 2021-04-26T08:16:41.157

We can achieve this with simple reduce like below.

const data =[{  a: 1,  created_on: '2021-04-23 04:00:00',}, {  b: 1,  created_on: '2021-04-24 09:03:01',}, {  b: 1,  created_on: '2021-04-24 13:03:01',}];

const allSlots = ['00:00-04:00', '04:00-08:00', '08:00-12:00', '12:00-16:00','16:00-20:00','20:00-24:00'].map(ele => ele.split('-'));




const result = data.reduce((acc, ele) => {
  // use can use format() to custom formats
  const [date, time] =ele.created_on.split(' ');
  const slot = allSlots.find(slot => slot[0] <= time && slot[1] >= time );
  if (!acc[date]) {
    acc[date] = {};
  }
  const key = `${slot[0]}-${slot[1]}`;
  if (!acc[date][key]) {
    acc[date][key] = [];
  }
  acc[date][key].push(ele);
  return acc;
}, {});

console.log(JSON.stringify(result))

group by array of objects with condition and custom key

3 Answers3

Vanilla JS

Using Array#reduce with Map.

Screenshot of the output

Using `Array#reduce` with `Map`.