Question

Usually while sorting you do:

if (x < y) return -1
else if (x > y) return 1
else return 0

or

return ((x > y) ? 1 : ((x < y)) ? -1 : 0))

Two comparisons for what seems can be accomplished with only one. In assembly all you have to do is subtract both to a register, check if is negative, check if is zero. The problem is in javascript if we were to subtract:

var sub = (x - y);
return (sub == 0 ? 0 : ((sub < 0) ? -1 : 1))

This would end up with even more code to be executed.

So, some questions:

• Is there a way of simplifying or speedying this in javascript?
• Can compiled javascript interpretors like chrome’s optimize this kind of comparison?
• What about other languages?

Answer 1

In Javascript, sort does not have to return -1, 0 or 1. It can return any number. This means that you only need to subtract one number from the other to compare them.

The MDC docs for Array.sort suggest this implementation:

function compareNumbers(a, b)
{
  return a - b;
}

var nums = [34, 56, 1, 42, 63];
nums.sort(compareNumbers);
// [1, 34, 42, 56, 63]