Sorting in [removed] Shouldn't returning a boolean be enough for a comparison function?

Question

I have always successfully sorted my arrays like this (when I did not want the standard lexicographic ordering):

var arr = […] // some numbers or so
arr.sort         


        

Answer 1

The sort function expects a function that expects two arguments a and b, and returns:

• A negative number if a comes before b
• A positive number if a comes after b
• Zero if relative order of a and b does not matter

In order to sort numbers in ascending order return a - b will produce the correct return values; for example:

a    b    ret
1    2    -1
3    2     1
2    2     0

On the other hand return a > b produces the following return values:

a    b    ret      implied
1    2    false    0
3    2    true     1
2    2    false    0

In the above example, the sort function is told that 1 and 2 are same (and placing 1 before 2 or 2 before 1 does not matter). This will produce incorrect result, for example (in Chrome 49):

console.log([5, 8, 7, 1, 2, 3, 4, 6, 9, 10, 11, 12, 13].sort(function(a, b) {
    return a > b;
}));
// [4, 5, 3, 1, 2, 6, 7, 8, 9, 10, 11, 12, 13]