31

I'm trying to sort an array of arrays with integers inside, for example:

var array = [[123, 3], [745, 4], [643, 5], [643, 2]];

How can I sort it in order to return something like the following?

array = [[745, 4], [643, 2], [643, 5], [123, 3]];
Peter Mortensen
  • 30,738
  • 21
  • 105
  • 131
Inês
  • 423
  • 1
  • 5
  • 7
  • 2
    Are you sorting by the first element in each array, or the largest element in each array? – mhodges May 18 '18 at 15:59
  • 2
    Possible duplicate of [Sort an array with arrays in it by string](https://stackoverflow.com/questions/5435228/sort-an-array-with-arrays-in-it-by-string) – Frank Visaggio May 18 '18 at 16:01
  • @mhodges sorting by the first element in each array – Inês May 18 '18 at 16:02
  • Note that this is essentially the same as [Sorting objects by property values](/q/2466356/4642212). If you’re looking for sorting an array _based on another array_ (e.g. `const order = [ "red", "green", "blue" ];` defines the order and you want to sort `[ "blue", "green", "red" ]` according to `order`), then see [Sort array based on another array](/q/13304543/4642212). – Sebastian Simon Mar 15 '22 at 12:28

5 Answers5

57

You can pass a custom comparison function to Array.prototype.sort(), like so:

var sortedArray = array.sort(function(a, b) { return a - b; });

This would sort an array of integers in ascending order. The comparison function should return:

  • an integer that is less than 0 if you want a to appear before b
  • an integer that is greater than 0 if you want b to appear before a
  • 0 if a and b are the same

So, for this example you would want something like:

var sortedArray = array.sort(function(a, b) {
  return b[0] - a[0];
});

If you wanted to sort on both elements of each sub-array (ie. sort by the first element descending, then if they are the same then sort by the second element descending), you could do this:

var sortedArray = array.sort(function(a, b) {
  if (a[0] == b[0]) {
    return a[1] - b[1];
  }
  return b[0] - a[0];
});

See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort for more info.

Let Me Tink About It
  • 15,156
  • 21
  • 98
  • 207
Gordon Larrigan
  • 694
  • 1
  • 7
  • 3
  • 2
    I noticed that comparison operators can be applied to arrays and it works, however it's not documented anywhere, e.g. `[2, 2] > [1, 3]` is true and `[1, 0] > [0, 1]` is true... etc. – CMCDragonkai Oct 11 '21 at 03:27
  • +1 to @CMCDragonkai's comment. Using the `>` and `<` operators you can explicitly return `1, -1, or 0` from the compare function. – dustinbrownman Oct 12 '21 at 20:06
  • Please don't use the `<` operator - it isn't correct in all situations. The arrays are implicitly stringified via `.join(',')` before comparing (see https://stackoverflow.com/questions/8328908/javascript-surprising-array-comparison). This means that `[11, 2] < [2, 3] == true` which is not what you want. – cbreezier Aug 29 '23 at 05:50
12

You can use sort method and first sort by first elements and then by second.

var array = [[123, 3], [745, 4], [643, 5], [643, 2]];
array.sort(([a, b], [c, d]) => c - a || b - d);
console.log(array)
Nenad Vracar
  • 118,580
  • 15
  • 151
  • 176
8

Assuming you want to sort by the first index in your example, the sort function exists to solve your problem.

let ans = [[123, 3], [745, 4], [643, 5], [643, 2]].sort( (a, b) => {
  return b[0] - a[0]
})

console.log(ans)
Ricardo Pierre-Louis
  • 166
  • 1
  • 5
3

A solution for the arrays with generic lengths (not limited to 2 or equal) can be as below:

array.sort((a,b)=>
    {
        for(let i=0;i<a.length && i<b.length;i++){
            if(a[i]!==b[i]){
                return a[i]-b[i];
            }

        }
        return a.length-b.length;
    };
Sandeep Parashar
  • 197
  • 1
  • 14
0

If you want to sort sub array in ascending order as per first element, we can do :

arrayToSort.sort((a, b) =>a[0] - b[0]);
Vidhya
  • 79
  • 2
  • 6