code: function(mask) {
          var borders = ['border-top','border-right', 'border-bottom', 'border-left'];
          var res = {};
          for (var i = 0; i < 4; i++) {
              if (!(mask & bin(i))) res[borders[i]] = 'none';
          }
          return res;
      }
docs: Exclude borders with 'none-border
  
  @param mask
  @return {{}}