3 ms·

No, the compare function needs to be able to indicate when two values are equal, not just when one is smaller/larger than the other. Otherwise your sort functio

• kristianp 8y ago
  So someList.sort((a,b) => a => b) Would be better, because it produces a stable sort? `a - b` produces the same results, so equally valid?
  • Ajedi32 8y ago
    No. `(a,b) => a => b` cannot produce a stable sort in all scenarios. Would theoretically work fine for integers since there's no difference between any two instances of the same number, but consider: let arr = [ {number: 2, name: 'a'}, {number: 1, name: 'b'}, {number: 1, name: 'c'}, ] Now assume we want to sort arr with a compare function, and our sort function expects the compare function to return a boolean, not an integer. let compare = (a,b) => a.number => b.number compare(arr[0], arr[1]) //=> true, so the object named 'a' comes after 'b' compare(arr[1], arr[2]) //=> true, so the object named 'b' comes after 'c'? See the problem?
  • jwilk 8y ago
    (I'm assuming you meant "a >= b", not "a => b".) That's still not a consistent comparison function, so the results are implementation-defined. To be consistent, it's required, among others, that if cmp(a, b) == 0 then cmp(b, a) == 0. For "a >= b", this is not always true, e.g.: » cmp(0, 1) == 0 true » cmp(1, 0) == 0 false