我想实现个鼠标按下滚动速度加快

HTML code

<style>
body{ padding:0; margin:0;}
img{ width:100px; height:100px;}
.up,.down{ width:100px; height:20px; background:#9CC; text-align:center;}
</style>
<div class="up" id="up">向上</div>
<div id="scrollup" style=" width:100px; height:100px; overflow:hidden">
    <div id="scrollup1">
        <img src="image/person1.jpg" />
        <img src="image/person2.jpg" />
        <img src="image/person3.jpg" />
        <img src="image/person4.jpg" />
    </div>
    <div id="scrollup2"></div>
</div>
<div class="down" id="down">向下</div>
<script>
var speed = 10;
var scrollup= document.getElementById("scrollup");
var scrollup1 = document.getElementById("scrollup1");
var scrollup2 = document.getElementById("scrollup2");
    scrollup2.innerHTML = scrollup1.innerHTML;
function Marqueeup(){
    if(scrollup2.offsetTop == scrollup.scrollTop ){
        scrollup.scrollTop -= scrollup2.offsetHeight;
    }else{
        scrollup.scrollTop++;
    }
}
function Marqueedown(){
    if( scrollup.scrollTop ==0 ){
        scrollup.scrollTop += scrollup2.offsetHeight;
    }else{
        scrollup.scrollTop--;
    }
}
var mar = setInterval(Marqueeup,speed);

var up = document.getElementById("up");
var down = document.getElementById("down");
up.onclick = function(){
    clearInterval(mar);
    mar = setInterval(Marqueeup,speed);
}
down.onclick = function(){
    clearInterval(mar);
    mar = setInterval(Marqueedown,speed);
}

</script>

现在我实现了鼠标点击上下时 图片上下滚动。 但是我还想实现当鼠标左键按下时滚动速度变快那种效果。。求大神帮忙

写个onmousedown方法去控制下speed 应该就可以了。。

up.onmousedown = function () {
   
  clearInterval(mar);
  speed = 1;
  mar = setInterval(Marqueeup, speed);
  }
像这样

实现了 3Q