Sort JSON by sum of array in javascript

Question

I'm trying to sort some json in js. And I'm trying to sort by the sum of "numbers", in a descending order. So for this data, the second row data would be first, since the sum of "numbers" is larger. I figured out how to sort by anything else, but not by the sum.

{
   "rows":[
      {
         "key":0,
         "name":"whitelilac",
         "numbers":[
            10,
            40,
            5
         ],
         "options":[
            "yes",
            "no",
            "maybe"
         ],
         "comment":"content"
      },
      {
         "key":1,
         "name":"blacklilac",
         "numbers":[
            5000,
            10,
            20
         ],
         "options":[
            "yes",
            "no",
            "maybe"
         ],
         "comment":"content"
      }
   ],
   "more":false
}

Do know how to compute the sum of an array? If you can do that, why can't you just sort by that? — Barmar, Jun 29 '20 at 22:04
See https://stackoverflow.com/questions/1230233/how-to-find-the-sum-of-an-array-of-numbers for how to calculate the sum of an array. — Barmar, Jun 29 '20 at 22:04
This was my last attempt at sorting, which works for every key but "numbers": `function sortResults(prop, dec) {` `data.rows.sort(function(a, b) {` `if (dec) {` `return (b[prop] > a[prop]) ? 1 : ((b[prop] < a[prop]) ? -1 : 0);` `} else {` `return (a[prop] > b[prop]) ? 1 : ((a[prop] < b[prop]) ? -1 : 0);` `}` `});` `}` Can't make it work with `array.reduce((a, b) => a + b, 0)` basically. — WhiteLilac, Jun 29 '20 at 22:08

blex · Accepted Answer · 2020-06-29T23:15:12.130

First, we need to know how to calculate the sum of an Array of numbers. We can do that using reduce:

const numbers = [1, 2, 3];

const res = numbers.reduce((sum, n) => sum + n);

console.log(res); // 6

Then, we need to know how to sort an Array based on a function (with sort), and this is it:

const obj = {rows:[{key:0,name:"whitelilac",numbers:[10,40,5],options:["yes","no","maybe"],comment:"content"},{key:1,name:"blacklilac",numbers:[5e3,10,20],options:["yes","no","maybe"],comment:"content"}],more:!1};

function sumArray(arr) {
  return arr.reduce((sum, n) => sum + n);
}

function sortBySum(a, b) {
  return sumArray(b.numbers) - sumArray(a.numbers);
}

obj.rows.sort(sortBySum);

document.body.innerHTML = `<pre>${JSON.stringify(obj, 0, 2)}</pre>`;

If you don't want to mutate the original Object, you can use this trick:

const obj = {rows:[{key:0,name:"whitelilac",numbers:[10,40,5],options:["yes","no","maybe"],comment:"content"},{key:1,name:"blacklilac",numbers:[5e3,10,20],options:["yes","no","maybe"],comment:"content"}],more:!1};

function sumArray(arr) {
  return arr.reduce((sum, n) => sum + n);
}

function sortBySum(a, b) {
  return sumArray(b.numbers) - sumArray(a.numbers);
}

const sortedRows = [].concat(obj.rows).sort(sortBySum);

document.body.innerHTML = `
<h1>Original obj (unmodified)</h1>
<pre>${JSON.stringify(obj, 0, 2)}</pre>
<h1>Sorted rows array</h1>
<pre>${JSON.stringify(sortedRows, 0, 2)}</pre>
`;

@WhiteLilac That's how JS 's sort works :) But you can still do it without mutation, see my update (third snippet) — blex, Jun 29 '20 at 23:15

Hamza Rashid · Answer 2 · 2020-06-29T22:38:11.990

Solution

Support your JSON is available in data variable.

Use reduce and sort functions to get your desired output.

const data = {"rows":[{"key":0,"name":"whitelilac","numbers":[10,40,5],"options":["yes","no","maybe"],"comment":"content"},{"key":1,"name":"blacklilac","numbers":[5000,10,20],"options":["yes","no","maybe"],"comment":"content"}],"more":false};

const sum = el => el.reduce((sum, item) => sum + item);

data.rows.sort((a, b) => sum(a.numbers) - sum(b.numbers)); // ascending sort
console.log(data);

data.rows.sort((a, b) => sum(b.numbers) - sum(a.numbers)); // descending sort
console.log(data);

score -1 · Answer 3 · answered Jun 29 '20 at 22:10

-1

Use JS sort() & you can write your own custom comparison function: Ex-

obj.rows.sort(function(first, second){
//calc sum of numbers 
//return sumOfFirst - sumOfSecond 
}
)

answered Jun 29 '20 at 22:10

Anshul

94
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Sort JSON by sum of array in javascript

3 Answers3