docs: function getSparseArrayIndexes(arr, fromIndex, loop, fromRight) {
    var indexes = [], i;
    for (i in arr) {
      // istanbul ignore next
      if (isArrayIndex(i) && (loop || (fromRight ? i <= fromIndex : i >= fromIndex))) {
        indexes.push(+i);
      }
    }
    indexes.sort(function(a, b) {
      var aLoop = a > fromIndex;
      var bLoop = b > fromIndex;
      // This block cannot be reached unless ES5 methods are being shimmed.
      // istanbul ignore if
      if (aLoop !== bLoop) {
        return aLoop ? -1 : 1;
      }
      return a - b;
    });
    return indexes;
  }