Sort two dimensional array using javascript

Question

I'd like to sort a two dimensional array using javascript.

My array :

[
  ['1','6'],
  ['1','5'],
  ['2','3'],
  ['0','4'],
]

My sorting function :

// 1st sort
myArray.sort( function(a, b) {
  return a[0] - b[0];
});

// 2nd sort
myArray.sort( function(a, b) {
  return a[1] - b[1];
});

The result :

["2", "3"]
["0", "4"]
["1", "6"]
["1", "5"]

The result should be :

["0", "4"]
["1", "5"] // 5 before 6 and the left column is sorted
["1", "6"]
["2", "3"]

Try this: https://stackoverflow.com/questions/16096872/how-to-sort-2-dimensional-array-by-column-value — Kannan K, Jan 12 '18 at 10:16

gurvinder372 · Accepted Answer · 2018-01-12T10:26:33.643

9

Your second sort is overriding the sorting done by first sort and it is only keeping the second column sorted.

You don't need two sort functions, just include both in a single sort as

myArray.sort( function(a, b) {
  return (a[0] - b[0]) || (a[1] - b[1]);
});

or without braces

myArray.sort( function(a, b) {
  return a[0] - b[0] || a[1] - b[1];
});

Demo

var myArray = [
    ['1','6'],
    ['1','5'],
    ['2','3'],
    ['12','13'],
    ['0','4'],
];
myArray.sort(function(a, b) {
  return (a[0] - b[0]) || (a[1] - b[1]);
});

console.log(myArray);

edited Jan 12 '18 at 10:26

answered Jan 12 '18 at 10:15

gurvinder372

64,240
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@NinaScholz Sure, I added braces initially for better readability – gurvinder372 Jan 12 '18 at 10:17
1

@NinaScholz the precedence between `-` and `||` isn't obvious (although it is documented), so braces can help – Aaron Jan 12 '18 at 10:18
oh no. please do not use unary plusses for changing values to number because they are converted to number by using minus operator by default. – Nina Scholz Jan 12 '18 at 10:25
@NinaScholz You are right, I tested without unary plus and it worked as well. Thanks. – gurvinder372 Jan 12 '18 at 10:26

Nina Scholz · Answer 2 · 2018-01-12T19:04:29.353

6

You could use a different approach for an arbitrary length of the arrays.

This solution assumes, that all inner arrays have the same length.

var array = [['1','6', '1'], ['1','5', '1'], ['1','5', '2'], ['2','3', '0'], ['0','4', '0']];

array.sort(function (a, b) {
    var d;
    a.some((v, i) => d = v - b[i]);
    return d;
});

console.log(array.map(a => a.join(' ')));

edited Jan 12 '18 at 19:04

answered Jan 12 '18 at 10:22

Nina Scholz

351,820
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`var i = 0, res; while(!(res = a[i] - b[i++])); return res;` ... i still prefer imperative programming... – Jonas Wilms Jan 12 '18 at 10:35
@JonasW., right, another possibility, but no length check. it loops forever with equal arrays, value wise. – Nina Scholz Jan 12 '18 at 10:38

score 3 · Answer 3 · answered Jan 12 '18 at 10:17

3

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

Just sort after the second slot if the first ones are equal

answered Jan 12 '18 at 10:17

Jonas Wilms

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Sort two dimensional array using javascript

3 Answers3