sum values, and merge object values with the same id into a new array

Question

I have an item object that I receive from the server. Each item and its quantity has to be saved with the seller, however, at the time of showing on the screen, I need the values to be totaled independent of the seller in a new array.

[
    { code: 1, item: 'ball', salesman: 'Braan', quantity: 5, price: 10.00},
    { code: 1, item: 'shoe', salesman: 'Alex', quantity: 5, price: 20.00},
    { code: 1, item: 'ball', salesman: 'Max', quantity: 3, price: 10.00},
    { code: 1, item: 'shirt', salesman: 'Braan', quantity: 5, price: 15.00}
]

the desired output would be:

[
    { code: 1, item: 'ball', quantity: 8, price: 20.00},
    { code: 1, item: 'shoe', quantity: 5, price: 20.00},
    { code: 1, item: 'shirt', quantity: 5, price: 15.00}
]

Hi! Have you tried implementing this yourself? Add youd [mcve] and explain what is the problem you are facing. — Esko, Jan 16 '19 at 13:16
Possible duplicate of [Most efficient method to groupby on a array of objects](https://stackoverflow.com/questions/14446511/most-efficient-method-to-groupby-on-a-array-of-objects) — Cid, Jan 16 '19 at 13:31

Prince Hernandez · Answer 1 · 2019-01-16T13:53:34.853

2

basically you can remap your object to remove the salesman key.

const serverData = [{
    code: 1,
    item: 'ball',
    salesman: 'Braan',
    quantity: 5,
    price: 10.00
  },
  {
    code: 1,
    item: 'shoe',
    salesman: 'Alex',
    quantity: 5,
    price: 20.00
  },
  {
    code: 1,
    item: 'ball',
    salesman: 'Max',
    quantity: 3,
    price: 10.00
  },
  {
    code: 1,
    item: 'shirt',
    salesman: 'Braan',
    quantity: 5,
    price: 15.00
  }
]

const result = serverData
  .map((item, i, array) => {
    const defaultValue = {
      code: item.code,
      item: item.item,
      quantity: 0,
      price: 0
    }
    const finalValue = array
      .filter(other => other.item === item.item) //we filter the same items
      .reduce((accum, currentVal) => { //we reduce them into a single entry
        accum.quantity += currentVal.quantity;
        accum.price += currentVal.price;
        return accum;
      }, defaultValue);

    return finalValue;
  })
  .filter((item, thisIndex, array) => { //now our new array has duplicates, lets remove them
    const index = array.findIndex((otherItem, otherIndex) => otherItem.item === item.item && otherIndex !== thisIndex && otherIndex > thisIndex);

    return index === -1
  })

console.log(result)

edited Jan 16 '19 at 13:53

answered Jan 16 '19 at 13:21

Prince Hernandez

3,623
1
10
19

Can you please motivate why the map should be used ? Why filter is not the right choice for this ? – Andrei Todorut Jan 16 '19 at 13:22
@AndreiTodorut as I told you in another comment.... filter is to remove entries from an array, it is not to remove keys from the object (well, you can do it but it is an overkill to do the same stuff in a map) – Prince Hernandez Jan 16 '19 at 13:22
@AndreiTodorut also, why are you voting down the answer, if it is cleaner way to do it and it is also the fastest. – Prince Hernandez Jan 16 '19 at 13:23
No :)) I just pushed the upvote for both answers.. I don't know who was the one who pressed the down vote :)) – Andrei Todorut Jan 16 '19 at 13:24
Ah I know why it was downvoted. This doesn't give the expected result. – Cid Jan 16 '19 at 13:26
Sorry, maybe I was not specific in the title. I need to make a sum of the quantities and values of the items, the seller is indifferent to the view. – Christian Santos Grossi Jan 16 '19 at 13:28
@Cid you are correct as the OP states, I'll modify to fix it. – Prince Hernandez Jan 16 '19 at 13:29
OP check the current solution now, it solves your problem @AndreiTodorut there you have the usage of filter within a reduce and map :) – Prince Hernandez Jan 16 '19 at 13:54
@Cid now there is a more explained and complete solution. – Prince Hernandez Jan 16 '19 at 13:55

score 1 · Answer 2 · answered Jan 16 '19 at 13:30

You could reduce the array by grouping by item and assuming the same price.

var data = [{ code: 1, item: 'ball', salesman: 'Braan', quantity: 5, price: 10.00 }, { code: 1, item: 'shoe', salesman: 'Alex', quantity: 5, price: 20.00 }, { code: 1, item: 'ball', salesman: 'Max', quantity: 3, price: 10.00 }, { code: 1, item: 'shirt', salesman: 'Braan', quantity: 5, price: 15.00 }],
    result = data.reduce((r, { code, item, quantity, price }) => {
        var temp = r.find(o => o.item === item);
        if (!temp) {
            r.push({ code, item, quantity, price });
        } else {
            temp.quantity += quantity;
        }
        return r;
    }, []);

console.log(result)

score 0 · Answer 3 · answered Jan 16 '19 at 13:20

0

Simple use map function to create new array with object with reduced properties.

const arr = [
    { code: 1, item: 'ball', salesman: 'Braan', quantity: 5, price: 10.00},
    { code: 1, item: 'shoe', salesman: 'Alex', quantity: 5, price: 20.00},
    { code: 1, item: 'ball', salesman: 'Max', quantity: 3, price: 10.00},
    { code: 1, item: 'shirt', salesman: 'Braan', quantity: 5, price: 15.00}
];

const newArr = arr.map((obj) => {
  return {
    code: obj.code,
    quantity: obj.quantity,
    price: obj.price,
    item: obj.item
  }
})

console.log(newArr)

answered Jan 16 '19 at 13:20

Łukasz Blaszyński

1,536
1
8
13

why map and not filter ? – Andrei Todorut Jan 16 '19 at 13:20
1

@AndreiTodorut .... filter is to remove entries from an array, it is not to remove keys from the object (well, you can do it but it is an overkill to do the same stuff in a map) – Prince Hernandez Jan 16 '19 at 13:22
do you have any thoughts why map is used ? – Andrei Todorut Jan 16 '19 at 13:22
Its the simplest way to achieve that. As a result we need array with all elements, the length is the same but without one property. – Łukasz Blaszyński Jan 16 '19 at 13:23
(not my downvote) This doesn't give the expected result. – Cid Jan 16 '19 at 13:26

Avi · Answer 4 · 2019-01-16T14:06:54.097

Try this

og = [
  { code: 1, item: 'ball', salesman: 'Braan', quantity: 5, price: 10.00},
  { code: 1, item: 'shoe', salesman: 'Alex', quantity: 5, price: 20.00},
  { code: 1, item: 'ball', salesman: 'Max', quantity: 3, price: 10.00},
  { code: 1, item: 'shirt', salesman: 'Braan', quantity: 5, price: 15.00}
]

var filtered = {};
og.forEach(d => {
  x = filtered[d.item] || {};

  x = {
    code: d.code, 
    item: d.item, 
    quantity: (x.quantity || 0) + d.quantity, 
    price: (x.price || 0) + d.price
  }

  filtered[d.item] = x;
})


var fin = Object.keys(filtered).map(item => filtered[item])

console.log(fin)

Although I would suggest creating a map of all the item types, as that would be easily accessible.

score 0 · Answer 5 · answered Jan 16 '19 at 13:32

var result = [];
myArray.reduce(function(res, value) {
 if (!res[value.item]) {
res[value.item] = { price: 0,quantity: 0 };
result.push(res[value.item])
}
res[value.item].quantity += value.quantity;
res[value.item].price += value.price;

 return res;
 }, {});

console.log(result)

Christian Santos Grossi · Answer 6 · 2019-08-26T20:43:53.047

Thanks everyone, I solved it this way:

mergeEqualsItems(items: any[]) {
        const itemsCopy = JSON.parse(JSON.stringify(items));
        const map = new Map();
        const newArr = [];
        itemsCopy.forEach(elem => {
          if (map.get(elem.id)) {
            const elemMap = map.get(elem.id);
            elemMap.quantity = elemMap.quantity + elem.quantity;
            map.set(elem.id, elemMap);
          } else {
            delete elem.salesman;
            map.set(elem.id, elem);
          }
        });
        map.forEach(elem => newArr.push(elem));
        return newArr;
      }

sum values, and merge object values ​with the same id into a new array

6 Answers6

sum values, and merge object values with the same id into a new array