code: function ( type ) {
              if ( this._isClear ) return this;
      
              var scrollX = $B( this._target ).scrollLeft(),
                  scrollY = $B( this._target ).scrollTop(),
                  scrollW = this._getTargetSize( 'width' ),
                  scrollH = this._getTargetSize( 'height' );
      
              if ( scrollH > 0 ) {
                  if ( this._scrollY !== scrollY || scrollH !== this._scrollH ) {
                      this._scrollY = scrollY;
                      this._scrollH = scrollH;
      
                      if ( type === 'scrolltop' ) {
                          this._dispatch( type, scrollY, this._gap.top );
                      } else if ( type === 'scrollbottom' ) {
                          this._dispatch( type, scrollY, this._gap.top );
                      } else {
                          this._dispatch( 'scrolltop', scrollY, this._gap.top );
                          this._dispatch( 'scrollbottom', scrollY, scrollH - this._gap.bottom );
                      }
                  }
              }
      
              if ( scrollW > 0 ) {
                  if ( this._scrollX !== scrollX || scrollW !== this._scrollW ) {
                      this._scrollX = scrollX;
                      this._scrollW = scrollW;
      
                      if ( type === 'scrollleft' ) {
                          this._dispatch( type, scrollX, this._gap.left );
                      } else if ( type === 'scrollright' ) {
                          this._dispatch( type, scrollX, scrollW - this._gap.right );
                      } else {
                          this._dispatch( 'scrollleft', scrollX, this._gap.left );
                          this._dispatch( 'scrollright', scrollX, scrollW - this._gap.right );
                      }
                  }
              }
      
              return this;
          }
docs: 강제로 실행시켜 해당 조건에 부합되면 이벤트를 발생시킨다.
  @param {String}  type    발생시킬 event type, 설정하지 않으면 등록된 모든이벤트를 대상으로 한다.