支持键盘上下按键

areakeydown:function(e) {           
        var that = this; 
        document.onkeydown = function(event) { 
            var e = event || window.event, 
            ek = e.keyCode || e.which; 
            if(ek == 40) { that.area.scrollTop += 25 } 
            else if(ek == 38) { that.area.scrollTop -= 25 } 
            if(that.area.scrollTop > 0 && that.area.scrollTop < that.area.scrollHeight - that.area.offsetHeight){ duma.stopEvent(e); } 
            that.setBarPos(); 
        } 

    }, 

  for(var j=0; j<oArrLen; j++) { 
        new duma.BeautifyScrollBar(oArr[j],"dumascroll_arrow_up","dumascroll_arrow_up_a","dumascroll_handle","dumascroll_handle_a","dumascroll_arrow_down","dumascroll_arrow_down_a").run(); 
    }