需要事件 ： onmousedown onmousemove onmouseup
拖拽思路 ：
鼠标按下 onmousedown ： 记录鼠标按下时的内部偏移量
var disx = e.offsetX;
var disy = e.offsetY;
鼠标移动 onmousemove ： 设置被拖拽元素的left 和 top值
left = e.pageX - disx;
top = e.pageY - disy;
鼠标抬起 onmouseup ： 取消移动事件
对象.onmousemove = null
获取window窗口的宽度 ： window.innerWidth 高度 ： window.innerHeight
取消拖拽时的文字选中状态 window.getSelection?window.getSelection().removeAllRanges():document.selection.empty();
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>完美拖拽</title>
<style type="text/css">
html,
body {
overflow: hidden;
}
body,
div,
h2,
p {
margin: 0;
padding: 0;
}
body {
color: #fff;
background: #000;
font: 12px/2 Arial;
}
p {
padding: 0 10px;
margin-top: 10px;
}
span {
color: #ff0;
padding-left: 5px;
}
#box {
position: absolute;
300px;
height: 150px;
background: #333;
border: 2px solid #ccc;
top: 50%;
left: 50%;
margin: -75px 0 0 -150px;
}
#box h2 {
height: 25px;
cursor: move;
background: #222;
border-bottom: 2px solid #ccc;
text-align: right;
padding: 0 10px;
}
#box h2 a {
color: #fff;
font: 12px/25px Arial;
text-decoration: none;
outline: none;
}
</style>
<script type="text/javascript">
</script>
</head>
<body>
<div id="box" style="margin-left: 0px; margin-top: 0px; left: 533px; top: 231px;">
<h2><a href="javascript:;" id="a1">点击回放拖动轨迹</a></h2>
<p><strong>Drag:</strong><span>false</span></p>
<p><strong>offsetTop:</strong><span>231</span></p>
<p><strong>offsetLeft:</strong><span>533</span></p>
</div>
</body>
</html>
<script>
var oBox = document.getElementById("box");
var oA1 = document.getElementById("a1");
var arr = [];
oBox.onmousedown = function (e) {
var e = e || event;
//记录内部偏移量
var disx = e.offsetX;
var disy = e.offsetY;
//移动
oBox.onmousemove = function (e) {
var e = e || event;
var x = e.pageX - disx;
var y = e.pageY - disy;
var maxL = window.innerWidth - 300;
var maxT = window.innerHeight - 150;
// 边界处理
if (x < 0) {
x = 0;
} else if (x > maxL) {
x = maxL;
}
if (y < 0) {
y = 0;
} else if (y > maxT) {
y = maxT;
}
//设置div的left和top值
oBox.style.left = x + "px";
oBox.style.top = y + "px";
var aObj = {
aleft: x,
atop: y
}
arr.unshift(aObj);
}
document.onmouseup = function () {
oBox.onmousemove = null;
oA1.onclick = function () {
var num = 0;
var timer = null;
timer = setInterval(function () {
oBox.style.left = arr[num].aleft + "px";
oBox.style.top = arr[num].atop + "px";
num++;
if (num == arr.length) {
clearInterval(timer);
arr = [];
return;
}
}, 50)
}
}
return false;
}
</script>