_getAffixTypeScrollingDown(){
        var dims = this.dimensions;
        var sidebarBottom = dims.sidebarHeight + dims.containerTop;
        var colliderTop = dims.viewportTop + dims.topSpacing;
        var colliderBottom = dims.viewportBottom - dims.bottomSpacing;
        var affixType = this.affixedType;
        
        if( this.isSidebarFitsViewport() ){
          if( dims.sidebarHeight + colliderTop >= dims.containerBottom ){
            dims.translateY = dims.containerBottom - sidebarBottom;
            affixType = 'CONTAINER-BOTTOM'; 

          } else if( colliderTop >= dims.containerTop ){
            dims.translateY = colliderTop - dims.containerTop;
            affixType = 'VIEWPORT-TOP';
          }
        } else {
          if( dims.containerBottom <= colliderBottom ){
            dims.translateY = dims.containerBottom - sidebarBottom; 
            affixType = 'CONTAINER-BOTTOM';    

          } else if( sidebarBottom + dims.translateY <= colliderBottom ){
            dims.translateY = colliderBottom - sidebarBottom;
            affixType = 'VIEWPORT-BOTTOM';
          
          } else if( dims.containerTop + dims.translateY <= colliderTop &&
            (0 !== dims.translateY && dims.maxTranslateY !== dims.translateY) ){
            affixType = 'VIEWPORT-UNBOTTOM';
          }
        }

        return affixType;
      }
Get affix type while scrolling down.
@private
@return {String} - Proper affix type of scrolling down direction.