Simple way to sort 2d array in Javascript?

Question

I have a 2d array like this:

[[0,23],[19,30],[6,47],[5,59],[1,56],[1,20],[19,10]]

How can I sort that based on the value of pairs like this:

[[0,23],[1,20],[1,56],[5,59],[6,47],[19,10],[19,30]]

Here is my attempt:

let arr = [[0,23],[19,30],[6,47],[5,59],[1,56],[1,20],[19,10]];
let result = arr
              .map(a => `${a[0]}.${a[1]}`)
              .sort()
              .map(a => [parseInt(a.split('.')[0]),parseInt(a.split('.')[1])]);
console.log(result);

.as-console-row-code {
  white-space: initial !important;
}

The below code still gives wrong result. Any advice for a simple solution?

`.sort((a,b) => a-b)` .default sort looks at the first letter in string — cmgchess, Apr 16 '23 at 17:33
This task is not clear, as I see you need to sort by the first element in the subarray, am I right? — Faust Life, Apr 16 '23 at 17:47
@FaustLife When the first subelement is the same, the second subelement is considered to be sorted as well. — Jordy, Apr 16 '23 at 17:50

score 6 · Accepted Answer · answered Apr 16 '23 at 17:38

6

You could sort by the delta of the first and second index values.

const array = [[0, 23], [19, 30], [6, 47], [5, 59], [1, 56], [1, 20], [19, 10]];

array.sort((a, b) => a[0] - b[0] || a[1] - b[1]);

console.log(array);

answered Apr 16 '23 at 17:38

Nina Scholz

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score 1 · Answer 2 · answered Apr 16 '23 at 17:41

let arr = [[0,23],[19,30],[6,47],[5,59],[1,56],[1,20],[19,10]];
let result = arr
             // .map(a => `${a[0]}.${a[1]}`)
              .sort((a,b)=> {
               if (a[0] === b[0]) {
                  return a[1] - b[1];
                } else {
                  return a[0] - b[0];
                } 
              
              })
            //  .map(a => [parseInt(a.split('.')[0]),parseInt(a.split('.')[1])]);
console.log(result);

.as-console-row-code {
  white-space: initial !important;
}

I have commented the map statemens not to convert them into strings. that makes it sorted lexicographically. We can use custom sort function here as shown above

score 1 · Answer 3 · answered Apr 16 '23 at 17:46

Similar to this answer, but works for inner number arrays of any length (not just 2 elements):

function sortByNumberElements(arrA, arrB) {
  let diff = 0;
  const length = Math.min(arrA.length, arrB.length);
  for (let i = 0; i < length; i += 1) {
    diff = arrA[i] - arrB[i];
    if (diff) break;
  }
  return diff;
}

const input = [[0,23],[19,30],[6,47],[5,59],[1,56],[1,20],[19,10]];
input.sort(sortByNumberElements);

const expected = [[0,23],[1,20],[1,56],[5,59],[6,47],[19,10],[19,30]];

console.log("Equal?", JSON.stringify(input) === JSON.stringify(expected));

score 0 · Answer 4 · answered Apr 16 '23 at 18:07

The original question approach with added destructuring:

    const arr = [[0, 23], [19, 30], [6, 47], [5, 59], [1, 56], [1, 20], [19, 10]];
    
    const result = arr
      .map(([a, b]) => [a, b, a + b / 100])
      .sort(([, , key1], [, , key2]) => key1 - key2)
      .map(([a, b]) => [a, b]);
    
    console.log(result)

Simple way to sort 2d array in Javascript?

4 Answers4