sort multidimensional array javascript

Question

I would like to sort a multidimensional array of doubles.

The array looks like this : [[1,2],[2,3],[5,6],[8,9]]

I would like to sort it by the X value, and keep the x,y values paired.

I searched the site for multidimentional sorting and found threads like these where the sort function is modified like so:

location.sort(function(a,b) {

  // assuming distance is always a valid integer
  return parseInt(a.distance,10) - parseInt(b.distance,10);

});

I'm not sure how to modify this function to work for me, however.

Mukesh Soni · Accepted Answer · 2013-08-01 14:50:46Z

5

Just compare the array values -

var myarray =  [[1,2],[2,3],[5,6],[8,9]];

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

answered Aug 1, 2013 at 14:50

Mukesh Soni

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1 Comment

tbogatchev Over a year ago

Thanks, I guess that was pretty obvious!

Paul · Accepted Answer · 2013-08-01 14:52:03Z

2

You just need to compare the parts of a and b that you want to. With numbers you can use their difference:

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

Note that the array you provided already is sorted by the first value in each array. If you want to sort in descending order instead you can do this:

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

edited Aug 1, 2013 at 14:52

answered Aug 1, 2013 at 14:50

Paul

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Comments

MDEV · Accepted Answer · 2013-08-01 15:01:51Z

1

The safest way of achieving this is to do what you have in your question, but with numeric keys:

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

If by some chance the first element of each child array is always a single digit:

location.sort(); 
//only works if first element in child arrays are single digit (0-9)
//as in the example: [[1,2],[2,3],[5,6],[8,9]]
//[[1,2],[22,3],[5,6],[8,9]] - will not work as 22 is not a single digit

edited Aug 1, 2013 at 15:01

answered Aug 1, 2013 at 14:51

MDEV

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4 Comments

Evan Davis Over a year ago

Maybe useful as a comment, but this answer is going to confuse somebody.

MDEV Over a year ago

@Mathletics It's an answer - if the first element (x) is a single digit location.sort() works. How is that not a solution?

Evan Davis Over a year ago

Some noob is going to read that, miss the part about single digits (not understanding that sort, by default, is a string compare, which is why that works), and end up asking another question that could be easily answered by reading MDN.

MDEV Over a year ago

@Mathletics I've tried to make it more obvious - however I feel it's worth keeping there as it is much simpler to read and less code to manage (when possible to safely use)

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