Group and sum of an array of objects based on number key

Question

I am trying to create a statistical pie chart. As a http response i am getting a list from server using which i need to draw a pie chart.

For example: Data received:

[{1: 9, 2: 7}, {3:8, 2: 1}, {1:8, 5:9}, {2:3, 3:1}]

This is the desired output:

[{x: 1, y: 17}, {x: 2, y:10}, {x: 3, y: 9}, {x: 5, y: 9}]

Please note: x is the key and y is sum of similar key values

I have tried data.forEach((item, index) => {}). After writing this, I am actually getting no lead about how I can combine Object.keys(item), Object.values(item) and Object.values(item).reduce((a,b)=> return a+b;)

This may sound silly question, but any help would be appreciated. :)

@Andreas, data.forEach((item, index) => {}) After writing this i am actually getting no lead about how i can combine Object.keys(item), Object.values(item) and Object.values(item).reduce((a,b)=> return a+b;) else i would have posted. — TrickOrTreat
– TrickOrTreat, Commented Jul 8, 2019 at 8:00

adiga · Accepted Answer · 2019-07-08 08:07:49Z

2

You could reduce the array. Create an accumulator object with each number as key and and object with x and y keys as it's value. Loop through each object and update the y value based on the number. Then use Object.values() on the object returned to get the values of the accumulator as an array

const input = [{1: 9, 2: 7}, {3:8, 2: 1}, {1:8, 5:9}, {2:3, 3:1}]

const grouped = input.reduce((acc, obj) => {
  for (const x in obj) {
    acc[x] = acc[x] || { x , y: 0 }
    acc[x].y += obj[x]
  }
  return acc;
}, {})

console.log(Object.values(grouped))

edited Jul 8, 2019 at 8:07

answered Jul 8, 2019 at 8:02

adiga

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Nina Scholz · Accepted Answer · 2019-07-08 08:24:51Z

0

You could look for same key and update or insert a new object.

This approach does not change the order of the keys.

var data = [{ 1: 9, 2: 7 }, { 3: 8, 2: 1 }, { 1: 8, 5: 9 }, { 2: 3, 3: 1 }] ,
    result = data.reduce((r, o) => {
        Object.entries(o).forEach(([x, y]) => {
            var temp = r.find(o => o.x === x);
            if (temp) temp.y += y;
            else r.push({ x, y });
        });        
        return r;
    }, []);

console.log(result);

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

edited Jul 8, 2019 at 8:24

answered Jul 8, 2019 at 8:05

Nina Scholz

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