code: function(_list,_low,_high){
              if (_low>_high) return -1;
              var _middle = Math.ceil((_low+_high)/2),
                  _result = _docheck(_list[_middle],_middle,_list);
              if (_result==0)
                  return _middle;
              if (_result<0)
                  return _doSearch(_list,_low,_middle-1);
              return _doSearch(_list,_middle+1,_high);
          }
docs: do binary search