Min/max index? Min/max element? about d3-array

[mbostock]

Another thought is a “scan” method that takes a comparator and returns the index of the least element according to the comparator. Sort of like bisect, but in linear time for unsorted arrays.

var array = [{foo: 42}, {foo: 91}];
scan(array, function(a, b) { return a.foo - b.foo; }); // 0
scan(array, function(a, b) { return b.foo - a.foo; }); // 1

[mbostock]

Heh, I’m caught in a time loop! In d3/d3@0b1b9fb, I removed d3.first and d3.last (see d3/d3#420). The first was implemented as:

function first(array, f) {
  var i = 0, n = array.length, a = array[0], b;
  if (arguments.length === 1) f = ascending;
  while (++i < n) {
    if (f.call(array, a, b = array[i]) > 0) {
      a = b;
    }
  }
  return a;
}

But this returns the first (or last) value, not the index. Also, I don’t see a great reason to have both a first and a last method given that you can just invert the comparator.