拖拽box1元素
拖拽的流程：
- 当鼠标在被拖拽元素上按下时，开始拖拽onmousedown
- 当鼠标移动时被拖拽元素跟随鼠标移动onmousgmove
- 当鼠标松开时，被拖拽元素固定在当前位置onmouseup
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style>
#box1{
width: 100px;
height: 100px;
background-color: red;
position: absolute;
}
#box2{
width: 100px;
height: 100px;
background-color: yellow;
position: absolute;
left: 200px;
top: 200px;
}
</style>
</head>
<body>
我是body的内容
<div id="box1"></div>
<div id="box2"></div>
</body>
<script>
//获取box1
var box1=document.getElementById("box1");
//为box1绑定一个鼠标按下事件
box1.onmousedown=function(event){
//setCapture() 只有IE支持，火狐浏览器调用不报错，Chrome调用报错
box1.setCapture && box1.setCapture();
event=event || window.event;
//div的偏移量 鼠标.clientX-box1.offsetLeft;
//div的偏移量 鼠标.clientY-box1.offsetTop;
var ol=event.clientX-box1.offsetLeft;
var ot=event.clientY-box1.offsetTop;
//为document绑定一个onmousemove事件
//当鼠标在被拖拽元素上按下时，开始拖拽 onmousedown
document.onmousemove=function(event){
event=event || window.event;
//当鼠标移动时被拖拽元素跟随鼠标移动onmousemove
//获取鼠标的坐标
var left=event.clientX-ol;
var top=event.clientY-ot;
//修改box1的位置
box1.style.left=left+"px";
box1.style.top=top+"px";
};
//为document绑定一个鼠标松开事件
document.onmouseup=function(){
//当鼠标松开时，被拖拽元素固定在当前位置 onmouseup
//取消document的onmousemove事件
document.onmousemove=null;
//取消document的onmouseup事件
document.onmouseup=null;
//当鼠标松开时，取消对事件的捕获
box1.releaseCapture && box1.releaseCapture();
};
//当我们拖拽一个网页中的内容时，浏览器会默认去搜索引擎中搜索内容，此时会导致拖拽功能的异常，这个是浏览器提供的默认行为，
//如果不希望发生这个行为，则可以通过return false来取消默认行为
//IE不能使用，用setCapture()
return false;
};
</script>
</html>
将函数提取出来为drag()函数，可任意调用和拖拽元素
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style>
#box1 {
width: 100px;
height: 100px;
background-color: red;
position: absolute;
}
#box2 {
width: 100px;
height: 100px;
background-color: yellow;
position: absolute;
left: 200px;
top: 200px;
}
</style>
</head>
<body>
我是body的内容
<div id="box1"></div>
<div id="box2"></div>
</body>
<script>
function drag(obj) {
obj.onmousedown = function(event) {
obj.setCapture && obj.setCapture();
event = event || window.event;
var ol = event.clientX - obj.offsetLeft;
var ot = event.clientY - obj.offsetTop;
document.onmousemove = function(event) {
event = event || window.event;
var left = event.clientX - ol;
var top = event.clientY - ot;
obj.style.left = left + "px";
obj.style.top = top + "px";
};
document.onmouseup = function() {
document.onmousemove = null;
document.onmouseup = null;
box1.releaseCapture && box1.releaseCapture();
};
return false;
};
}
//获取box1
var box1 = document.getElementById("box1");
//为box1绑定一个鼠标按下事件
drag(box1);
//获取box2
var box2 = document.getElementById("box2");
//为box2绑定一个鼠标按下事件
drag(box2);
</script>
</html>
