JavaScript create array of Object structure

Question

Here is my problem:

I have a JSON structure as below

[{
    "groupid": 29,
    "percentage": 14
}, {
    "groupid": 29,
    "percentage": 22
}, {
    "groupid": 59,
    "percentage": 66,
}]

and i need to convert that into as below using Javascript.

{
    "29": [14, 22],
    "59": [66]
}

Can you please show what you've been trying?

Phil
– Phil

2018-10-31 02:59:57 +00:00
Commented Oct 31, 2018 at 2:59 — Phil
– Phil, Commented Oct 31, 2018 at 2:59

CertainPerformance · Accepted Answer · 2018-10-31 03:01:04Z

4

reduce the input into an object. On each iteration, create an array at the groupid key in the accumulator object if it doesn't exist yet, and then push to the array:

const input = [{
    "groupid": 29,
    "percentage": 14
}, {
    "groupid": 29,
    "percentage": 22
}, {
    "groupid": 59,
    "percentage": 66,
}];
const output = input.reduce((a, { groupid, percentage }) => {
  if (!a[groupid]) a[groupid] = [];
  a[groupid].push(percentage);
  return a;
}, {});
console.log(output);

answered Oct 31, 2018 at 3:01

CertainPerformance

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