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<!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>拖拽</title>
<style>
#ball {
width: 50px;
height: 50px;
background-color: lightpink;
border-radius: 50%;
box-shadow: 2px 2px 1px #888;
position:absolute;
}
</style>
</head>
<body>
<div id="ball"></div>
<script>
// onmousedown: 选择, onmouseover: 移动, onmouseup:放下
var ball = document.getElementById('ball');
// 选中这个小球
// onmousedown
//找到小球的位置:
// 当前鼠标到小球边沿的距离相对是不变的,变得只是小球到左边与顶部的距离
// 这个不变的距离 ,是鼠标点击下去的一瞬间就确定了,就可以求出来了
// 根据当前鼠标到当前可视区的距离
// 求出鼠标当前位置
ball.onmousedown = function (event) {
var x = event.clientX - this.offsetLeft;
var y = event.clientY - this.offsetTop;
console.log(x, y); // offsetLeft只读,返回数值
// 移太快,鼠标跑出小球了,怎么办, 应该把事件添加到整个文档就可以了,再快, 也不会跑出浏览器窗口吧
// ball.onmousemove = function (event) {
document.onmousemove = function (event) {
ball.style.left = event.clientX - x + 'px';
console.log(ball.style.left); // 注意返回的是字符串
ball.style.top = event.clientY - y + 'px';
}
// ball.onmouseup = function () {
document.onmouseup = function () {
// ball.onmousemove = null;
document.onmousemove = null;
}
}
</script>
</body>
</html>点击 "运行实例" 按钮查看在线实例
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