实现滚动条

相关代码：
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title></title>
    <style type="text/css">
        *{
            margin: 0;
            padding: 0;
        }
        html,body{
            height: 100%;
            overflow: hidden;
        }
        #wrap{
            position: absolute;
            top: 0;
            right: 0;
            width: 20px;
            height: 100%;
            background-color: #9ACD32;
        }
        #inner{
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;

            background-color: chocolate;
        }

        #content{
            position: absolute;
        }
    </style>
</head>
<body>
    <div id="content"></div>
    <div id="wrap">
        <div id="inner"></div>
    </div>
</body>
<script type="text/javascript">
    var inner=document.getElementById('inner');
    var content=document.getElementById('content');

    //添加文本
    for(var i=0;i<=1000;i++){
        content.innerHTML+=i+'<br>';
    }

    //滚动条的高度
    var scaleH=document.documentElement.clientHeight/content.offsetHeight;

    inner.style.height=scaleH*document.documentElement.clientHeight+'px';

    //定义目标元素的初始位置
    var eleY=0;
    //定义鼠标的初始位置
    var mouseS=0;

    //目标元素绑定鼠标点击事件
    inner.onmousedown=function (event) {
        //获取目标元素的初始位置
        eleY=inner.offsetTop;
        //鼠标的初始位置
        mouseS=event.clientY;
        document.onmousemove=function (event) {
            //鼠标的结束位置
            var mouseE=event.clientY;
            //鼠标的差
            var disY=mouseE-mouseS;

            //目标元素的终止位置
            var top=disY+eleY;

            //范围限定
            var topM=document.documentElement.clientHeight-inner.offsetHeight;
            if(top<0){
                top=0;
            }else if(top>topM){
                top=topM;
            };
            inner.style.top=top +'px';

            var scale=top/document.documentElement.clientHeight;
            content.style.top=-scale*(content.offsetHeight-document.documentElement.clientHeight)+'px';
        }
        document.onmouseup=function () {
            //dom0解绑
            document.onmousemove=document.onmouseup=null;

        }
        //清除系统默认行为
        return false;
    }
</script>
</html>
来源：CSDN
作者：gzlxing
链接：https://blog.csdn.net/qq_40238154/article/details/78738707
标签
var