目标：
让一个网页上的小窗口可以被鼠标拖曳带动
效果：
拖曳前：
1743169706881.png
拖曳后：
1743169678827.png
代码展示：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<style>
#box {
width: 200px;
height: 200px;
background-color: aqua;
position: absolute;
}
</style>
<body>
<div id="box"></div>
<script>
let box = document.getElementById("box")
box.onmousedown = function (e) {
let ox = e.offsetX
let oy = e.offsetY
document.onmousemove = function (e2) {
let cx = e2.clientX
let cy = e2.clientY
let _left = cx - ox
let _top = cy - oy
//边界判断
if (_left < 0) { //左边
_left = 0
}
if(_top < 0){//上边
_top = 0
}
//右边
if(_left > document.documentElement.clientWidth - box.offsetWidth){
_left = document.documentElement.clientWidth - box.offsetWidth
}
//下边
if(_top > document.documentElement.clientHeight - box.offsetHeight){
_top = document.documentElement.clientHeight - box.offsetHeight
}
box.style.left = _left + "px"
box.style.top = _top + "px"
}
}
document.onmouseup = function () {
document.onmousemove = null
}
</script>
</body>
</html>
