code: function indexInRange(index, rangeLength) {
          var range = calculateRange(rangeLength);
          if (index >= range.min && index <= range.max) {
              return true;
          }
          return false;
      }
docs: Returns true if the given index is in the page load range, and false otherwise
  @param   {int} index The page index
  @param   {int} rangeLength The page range length
  @returns {bool}      Whether the page index is in the page load range
  @private