How to map and group array of objects

Question

I'm building an application with Node.js, Express, Postgres and Sequelize.

I get a response that looks like this:

[
    {
        "id": 101,
        "type": 0,
        "bookings": [
            {
                "date": "2019-04-15T02:00:00.000Z"
            }
        ]
    },
    {
        "id": 102,
        "type": 4,
        "bookings": [
            {
                "date": "2019-04-17T02:00:00.000Z"
            }
        ]
    },
    {
        "id": 103,
        "type": 0,
        "bookings": [
            {
                "date": "2019-04-15T02:00:00.000Z"
            }
        ]
    },
    {
        "id": 104,
        "type": 0,
        "bookings": [
            {
                "date": "2019-04-17T02:00:00.000Z"
            }
        ]
    }
]

I want to group all the events that happen on the same date.

I tried

_.forEach(response, function(value) {
    _.groupBy(value, value.bookings[0].date)
})

but it doesn't work.

How can I map and group an array?

Eventually I want to have an object (or array) that looks something like this:

{
    2019-04-15: [
        { id: 101, type: 0 }, { id: 103, type: 0}
    ],
    2019-04-17: [
        { id: 102, type: 4 }, { id: 104, type: 0}
    ]
}

Can those bookings arrays have more than a single date-containing object? — Scott Sauyet
– Scott Sauyet, Commented Apr 12, 2019 at 1:51
At that point no. Dates can be confirmed and proposed. In the query I return only confirmed dates - always only one object. — Tom Bom
– Tom Bom, Commented Apr 12, 2019 at 1:56

Code Maniac · Accepted Answer · 2019-04-12 01:47:03Z

4

You can use reduce

let data = [{"id": 101,"type": 0,"bookings": [{"date": "2019-04-15T02:00:00.000Z"}]},{"id": 102,"type": 4,"bookings": [{"date": "2019-04-17T02:00:00.000Z"}]},{"id": 103,"type": 0,"bookings": [{"date": "2019-04-15T02:00:00.000Z"}]},{"id": 104,"type": 0,"bookings": [{"date": "2019-04-17T02:00:00.000Z"}]}]

let op = data.reduce((op,{bookings,...rest}) => {
  let key = bookings[0].date.split('T',1)[0]
  op[key] = op[key] || []
  op[key].push(rest)
  return op
},{})

console.log(op)

answered Apr 12, 2019 at 1:47

Code Maniac

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Comments

Ele · Accepted Answer · 2019-04-12 02:08:05Z

You can use the function reduce for grouping the objects by date.

This is assuming the array has only one index.

let arr = [    {        "id": 101,        "type": 0,        "bookings": [            {                "date": "2019-04-15T02:00:00.000Z"            }        ]    },    {        "id": 102,        "type": 4,        "bookings": [            {                "date": "2019-04-17T02:00:00.000Z"            }        ]    },    {        "id": 103,        "type": 0,        "bookings": [            {                "date": "2019-04-15T02:00:00.000Z"            }        ]    },    {        "id": 104,        "type": 0,        "bookings": [            {                "date": "2019-04-17T02:00:00.000Z"            }        ]    }];

let result = arr.reduce((a, {id, type, bookings: [{date}]}) => {
  let key = date.substring(0, 10);
  (a[key] || (a[key] = [])).push({id, type});
  return a;
}, Object.create(null));


console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Steven Bell · Accepted Answer · 2019-04-12 02:16:06Z

You can also use this to accomplish what you're looking for.

let response = [
    {
        "id": 101,
        "type": 0,
        "bookings": [
            {
                "date": "2019-04-15T02:00:00.000Z"
            }
        ]
    },
    {
        "id": 102,
        "type": 4,
        "bookings": [
            {
                "date": "2019-04-17T02:00:00.000Z"
            }
        ]
    },
    {
        "id": 103,
        "type": 0,
        "bookings": [
            {
                "date": "2019-04-15T02:00:00.000Z"
            }
        ]
    },
    {
        "id": 104,
        "type": 0,
        "bookings": [
            {
                "date": "2019-04-17T02:00:00.000Z"
            }
        ]
    }
]

let dateGroupings = {};

response.forEach((v)=> {
  let date = v.bookings[0].date.substring(0,10)
  if (!dateGroupings[date]){
    dateGroupings[date] = [];
  }

  let obj = { 
    id: v.id,
    type: v.type
  };

  dateGroupings[date].push(obj); 

})

Jordan · Accepted Answer · 2019-04-12 02:17:13Z

Well i didn't see that many answers but since i did it too


const data = [
    {
        "id": 101,
        "type": 0,
        "bookings": [
            {
                "date": "2019-04-15T02:00:00.000Z"
            }
        ]
    },
    {
        "id": 102,
        "type": 4,
        "bookings": [
            {
                "date": "2019-04-17T02:00:00.000Z"
            }
        ]
    },
    {
        "id": 103,
        "type": 0,
        "bookings": [
            {
                "date": "2019-04-15T02:00:00.000Z"
            }
        ]
    },
    {
        "id": 104,
        "type": 0,
        "bookings": [
            {
                "date": "2019-04-17T02:00:00.000Z"
            }
        ]
    }
];

const bookingsByDate = {};

data.forEach((booking) => {    

    booking.bookings.forEach((bookingDate) => {
        const date = new Date(bookingDate.date);
        const day = date.getDate() < 10 ?  '0' + date.getDate(): date.getDate();
        const month = date.getMonth() < 10 ? '0' + date.getMonth(): date.getMonth();
        const year = date.getFullYear();

        const fullDate = year + '-' + month + '-' + day;

        if(!bookingsByDate[fullDate]) {
            bookingsByDate[fullDate] = [];
        }
        bookingsByDate[fullDate] = [
            ...bookingsByDate[fullDate],
            { 
                id: booking.id,
                type: booking.type,
            }
        ]
    });

})
console.log(bookingsByDate);

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