Function comparator

test/angular/1.3/angular.js:17856–17862

(o1, o2)

    return slice.call(array).sort(reverseComparator(comparator, reverseOrder));

    function comparator(o1, o2) {
      for (var i = 0; i < sortPredicate.length; i++) {
        var comp = sortPredicate[i](o1, o2);
        if (comp !== 0) return comp;
      }
      return 0;
    }
    function reverseComparator(comp, descending) {
      return descending
          ? function(a, b) {return comp(b,a);}