var demo = document.getElementById("demo");
var demo1 = document.getElementById("demo1");
var demo2 = document.getElementById("demo2");
var direct = 'left';
var speed=30;    //数值越大滚动速度越慢
var scrollspeed=1;

demo2.innerHTML = demo1.innerHTML
var MyMar = setInterval(Marquee,speed);
demo.onmouseover = function(){clearInterval(MyMar);}
demo.onmouseout = function(){MyMar = setInterval(Marquee,speed)}
function Marquee(){
    if (direct == 'left') {
        if(demo2.offsetWidth-demo.scrollLeft<=0)
            demo.scrollLeft-=demo1.offsetWidth
        else{
            demo.scrollLeft+=scrollspeed;
        }
    } else { 
        if(demo.scrollLeft<=0)
            demo.scrollLeft+=demo2.offsetWidth
        else{
            demo.scrollLeft=demo.scrollLeft-scrollspeed;
        }
    }
}

function m_left() {
    if(direct=='right')
    {
        scrollspeed=1;
            
    }
    else
    {
        scrollspeed++;
    }
    direct = 'left';  
   
//Marquee();
}

function m_right() {


    if(direct=='left')
    {
        scrollspeed=1;
           
    }
    else
    {
        scrollspeed++;

        //alert(speed);
    }
    direct = 'right';
    //Marquee();
}