<!DOCTYPE html><html lang="en"><head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>Document</title></head><body><div style="border :1px solid red; width :500px;height :300px ; overflow:hidden; margin:20px"> <div id="blackSquare" style="position: relative; width:50px; height:50px; background-color: black;cursor: pointer;color:#fff">wjw</div></div></body><script> window.onload = () => { //获取拖拽实验对象 let el=document.getElementById("blackSquare"); //在该对象上绑定鼠标点击事件 el.onmousedown = (e) => { //鼠标按下，计算鼠标触点距离元素左侧的距离 let disX = e.clientX - el.offsetLeft; let disY = e.clientY - el.offsetTop; document.onmousemove = function (e) { //计算需要移动的距离 let t = e.clientX - disX; let P = e.clientY - disY; //移动当前元素 if (t >= 0 && t <= window.innerWidth - el.offsetWidth) { el.style.left = t + 'px'; } //移动当前元素 if (P >= 0 && P <= window.innerHeight - el.offsetHeight ) { el.style.top = P + 'px'; } }; //鼠标松开时，注销鼠标事件，停止元素拖拽。 document.onmouseup = function (e) { document.onmousemove = null; document.onmouseup = null; }; } }</script></html>
