get the sum of items with two identical property value inside array object using javascript

Question

I have an array of objects:

var obj = [
  {name: 'a1', type: 't1', price: 10},
  {name: 'a1', type: 't1', price: 10},
  {name: 'a2', type: 't2', price: 10},
  {name: 'a1', type: 't2', price: 10},
];

I need to get this result:

[
  {name: 'a1', type: 't1', price: 20},
  {name: 'a1', type: 't2', price: 10},
  {name: 'a2', type: 't2', price: 10}
]

I want to sum the item if, and only if, the properties name and type match. Any idea?

Possible duplicate [What is the most efficient method to groupby on a JavaScript array of objects?](https://stackoverflow.com/questions/14446511/what-is-the-most-efficient-method-to-groupby-on-a-javascript-array-of-objects) — Dean, May 17 '18 at 06:57
@HarishSoni never mind the question, i just need to get the result though — muimui, May 17 '18 at 06:59
When people doesn't understand your question, how people give you the result. — Dean, May 17 '18 at 06:59
Questions seeking debugging help ("why isn't this code working?") must include the desired behavior, a specific problem or error and the shortest code necessary to reproduce it in the question itself. Questions without a clear problem statement are not useful to other readers. — baao, May 17 '18 at 07:01
make an array with key of name|type and add the price. if needed you can split it up again afterwards . — Domenik Reitzner, May 17 '18 at 07:04
@Dean ok i want to get the sum of the price if both the 'name' and 'type' is the same. is that clear enough? thanks :) — muimui, May 17 '18 at 07:05

Eddie · Answer 1 · 2018-05-17T10:06:00.863

3

You can use reduce to group it into an object. Use Object.values to convert the object into array.

var obj = [
    {name: 'a1', type: 't1', price: 10},
    {name: 'a1', type: 't1', price: 10},
    {name: 'a2', type: 't2', price: 10},
    {name: 'a1', type: 't2', price: 10},
];

var result = Object.values(obj.reduce((c, v) => {
  let k = v.name + '-' + v.type;
  c[k] = c[k] || {...v, price: 0};
  c[k].price += v.price;
  return c;
}, {}));

console.log(result);

edited May 17 '18 at 10:06

answered May 17 '18 at 07:02

Eddie

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Happy to help :) – Eddie May 17 '18 at 07:09
@JonasW. If i wont spread the `v` on `Object.assign`, it actually change the value of `price` in `v`. Im open for suggestions :) – Eddie May 17 '18 at 09:12
Or I can just do this one `Object.assign({}, v, {price: 0});` And works just fine. – Eddie May 17 '18 at 09:15
`{...v, price: 0}` ?! – Jonas Wilms May 17 '18 at 10:04
1

Ohh nice. I didn't think about that. Thanks @JonasW. – Eddie May 17 '18 at 10:05

score 0 · Answer 2 · answered May 17 '18 at 07:02

You could reduce into a Map and turn it back into an array:

var obj = [
 {name: 'a1', type: 't1', price: 10},
 {name: 'a1', type: 't1', price: 10},
 {name: 'a2', type: 't2', price: 10},
 {name: 'a1', type: 't2', price: 10},
];

const map = obj.reduce((map, { name, type, price }) => {
  console.log('iter');
  const key = name + '_' + type;
  return map.set(key, (map.get(key) || 0) + price);
}, new Map());

const output = [...map.entries()].map(([key, val]) => {
  const [name, type] = key.split('_');
  return { name, type, price: val };
});
console.log(output);

score 0 · Answer 3 · answered May 17 '18 at 07:02

You can try following (sum and sort by name and type)

var obj = [
 {name: 'a1', type: 't1', price: 10},
 {name: 'a1', type: 't1', price: 10},
 {name: 'a2', type: 't2', price: 10},
 {name: 'a1', type: 't2', price: 10},
];

// First create the result object where sum of price is done
var result =  obj.reduce((a,c) => {
  if(a[c.name + "_" + c.type]) {
    a[c.name + "_" + c.type].price += c.price;
  } else {
    a[c.name + "_" + c.type] = c;
  }
  return a;
}, {});

// Get the values in an array
result = Object.values(result);

// Sort the array by name and then type
result.sort((a,b) => {
  if(a.name === b.name) return a.type.localeCompare(b.type);
  return a.name.localeCompare(b.name);
});

console.log(result);

score 0 · Answer 4 · answered May 17 '18 at 07:03

You can use of Array.reduce to build up a new array considering your requirements.

const obj = [{
    name: 'a1',
    type: 't1',
    price: 10,
  },
  {
    name: 'a1',
    type: 't1',
    price: 10,
  },
  {
    name: 'a2',
    type: 't2',
    price: 10,
  },
  {
    name: 'a1',
    type: 't2',
    price: 10,
  },
].reduce((tmp, x) => {
  // Look if there is already a matching item in tmp
  const findItem = tmp.find(y => y.name === x.name && y.type === x.type);

  // It's not inside
  if (!findItem) {
    tmp.push(x);

    return tmp;
  }

  // it is inside
  findItem.price += x.price;

  return tmp;
}, []);

console.log(obj);

get the sum of items with two identical property value inside array object using javascript

4 Answers4