不吃鱼的猫咪
不吃鱼的猫咪

js实现窗口拖拽效果


<html>

 <head>
 <meta charset="UTF-8">
 <title>title>
 <style type="text/css">
 #box {
 width: 300px;
 background-color: green;
 position: absolute;
 }
 h2{
 width:100%
}
 style>
 head>

 <body>
 <div id="box">
  <h2>窗口标题h2>
  <div class="content">
  内容
  div>
 div>
 body>
 <script type="text/javascript">
 var box = document.getElementById("box");
 var dragBar= box.getElementsByTagName('h2');
 //鼠标按下的函数
 dragBar.onmousedown = function(ev) {
    var oEvent = ev || event;
    //求出鼠标和box的位置差值
    var x = oEvent.clientX - box.offsetLeft;
    var y = oEvent.clientY - box.offsetTop;
    //鼠标移动的函数
    //把事件加在document上，解决因为鼠标移动太快时，
    //鼠标超过box后就没有了拖拽的效果的问题
    document.onmousemove = function(ev) {
        var oEvent = ev || event;
        //只能拖动窗口标题才能移动
        if(oEvent.target!=tit){
            return;
        }
        //保证拖拽框一直保持在浏览器窗口内部，不能被拖出的浏览器窗口的范围
        var l = oEvent.clientX - x;
        var t = oEvent.clientY - y;
        if(l < 0) {
            l = 0;

        } else if(l > document.documentElement.clientWidth - box.offsetWidth) {
            l = document.documentElement.clientWidth - box.offsetWidth;
        }
        if(t < 0) {
            t = 0;
        } else if(t > document.documentElement.clientHeight - box.offsetHeight) {
            t = document.documentElement.clientHeight - box.offsetHeight;
        }
        box.style.left = l + "px";
        box.style.top = t + "px";
    }
    //鼠标抬起的函数
    document.onmouseup = function() {
        document.onmousemove = null;
        document.onmouseup = null;
    }
    //火狐浏览器在拖拽空div时会出现bug
    //return false阻止默认事件，解决火狐的bug
    return false;
}
 script>

html>

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