Create distinct object based on the date from input array in js

Question

I have an 'orders' array that looks like this:

 [
   [
     ['2022-07-10', 300],
     ['2022-07-8', 350],
     ['2022-07-9', 400],
     ['2022-07-8', 206],
     ['2022-07-10', 300],
   ],
   [
     ['2022-07-7', 397],
     ['2022-07-9', 323],
     ['2022-07-8', 472],
     ['2022-07-7', 336],
     ['2022-07-10', 400],
   ],
 ];

what I want at the end is to have an array of objects containing distinct date and total is the sum of element with same dates:

[
   {date: '10/07/2022', total: 1000},
   {date: '08/07/2022', total: 1028},
   {date: '09/07/2022', total: 723},
   ...
];

Here is what I did and I was wondering if there is a better/shorter way to do that:

groupOrdersByDate(orders: any[]) {
    let res: any[] = [];

    orders.forEach((ar) => {
      ar.forEach((el: any) => {
        console.log(res);
        let dateOrder: string = new Date(el[0]).toLocaleDateString('fr');
        let found = res.some((e) => e.date === dateOrder);
        if (!found) {
          res.push({ date: dateOrder, total: el[1] });
        } else {
          let existingObj = res.find((el) => el.date === dateOrder);
          let indexx = res.findIndex((o) => {
            return o.date === existingObj.date;
          });
          existingObj.total = existingObj.total + el[1];
          res.splice(indexx, 1, existingObj);
        }
      });
    });
}

I was also wondering why is my commented console.log of my res array not empty? It shows values even though I did not pushed any elements to it yet ?

1) Your code seems readable to me, this should be ok. 2) I was also wondering why is my commented console.log of my res array not empty? Console values are passed as reference, hence you are seeing the recent values of res. — Rayon
– Rayon, Commented Aug 14, 2022 at 0:13

akuiper · Accepted Answer · 2022-08-14 00:37:31Z

1

It will be more efficient/concise if you store the results in an intermediate object so you don't have to find match for each element:

const orders = [
   [
     ['2022-07-10', 300],
     ['2022-07-8', 350],
     ['2022-07-9', 400],
     ['2022-07-8', 206],
     ['2022-07-10', 300],
   ],
   [
     ['2022-07-7', 397],
     ['2022-07-9', 323],
     ['2022-07-8', 472],
     ['2022-07-7', 336],
     ['2022-07-10', 400],
   ],
 ];
 
const _sum = {}
 
orders.forEach(arr => {
  arr.forEach(([date, quantity]) => {
    let dateOrder = new Date(date).toLocaleDateString('fr');
    _sum[dateOrder] = (_sum[dateOrder] ?? 0) + quantity;
  })
})

let results = Object.entries(_sum).map(([date, total]) => ({date, total}))

console.log(results)

answered Aug 14, 2022 at 0:37

akuiper

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