拖动

 <style>
        #move{
            width: 200px;
            height: 100px;
            background: red;
            position: absolute;
            left: 40%;
            top: 40%;
            cursor: pointer;
        }
    </style>

 <div id="move">
    </div>
    <script>
        /* onmousedown 鼠标按下
           onmouseup   鼠标松开
        */
        var move=document.getElementById("move")
        move.onmousedown=function(event){
            var clientX=event.clientX;
            var offsetX=this.offsetLeft;
            var spaceX=clientX-offsetX;
            var spaceY=event.clientY-this.offsetTop;
            document.onmousemove=function(event){
                let pageX=event.clientX;
                let left=pageX-spaceX;
                var top=event.clientY-spaceY;
                move.style.cssText=`left:${left}px;top:${top}px`
            }
        }
        move.onmouseup=function(){
            document.onmousemove=null;
        }
    </script>