code: function(data){
        var count =  5;
        var show = data.show = Math.floor( count/2 );
        data.current = data.current || 1;
        data.total = data.total || 1;
  
        this.$watch(['current', 'total'], function( current, total ){
          data.begin = current - show;
          data.end = current + show;
          if(data.begin < 2) data.begin = 2;
          if(data.end > data.total-1) data.end = data.total-1;
          if(current-data.begin <= 1) data.end = data.end + show + data.begin- current;
          if(data.end - current <= 1) data.begin = data.begin-show-current+ data.end;
        });
      }
docs: before init