Javascript 第十章

<html>
<head>
    <title></title>
    <style>
        #slideshow{width:256px;height: 256px;position:relative;overflow: hidden;}
    </style>
</head>
<body>
<h1>Web Design</h1>
<p>There are things you should know</p>
<ol id="linklist">
    <li><a href="1">1</a></li>
    <li><a href="2">2</a></li>
    <li><a href="3">3</a></li>
</ol>

<div id="slideshow">
    <img src="images/topics.jpg" alt="web design" id="preview">
</div>

<script>
    function addLoadEvent(func){
                var oldonload = window.onload;
               if (typeof oldonload != 'function') {
                    window.onload = func;
               }else{
                    window.onload = function(){
                    oldonload();
                    func();
                    }
               }
    }


    function prepareSlideShow(){
        var preview = document.getElementById("preview");
        preview.style.position = "absolute";
        preview.style.left = 0;
        preview.style.top = 0;
        var links = document.getElementsByTagName("a");
        for (var i = 0; i < links.length; i++) {
            links[i].onmouseover = function(){
                var order = parseInt(this.getAttribute("href"));
                movePreview("preview",(-256*(order-1)));
            }
        }

    }



    addLoadEvent(prepareSlideShow);


    function movePreview(id,xpos){
        var elem = document.getElementById(id);
        if (elem.movevent) {
            clearTimeout(elem.movevent);
        }
        var lpos = parseInt(elem.style.left),dist; 
        if (lpos == xpos) return true;
        /*每次移动1px速度太慢,所以每次移动差距的1/10,当差距< 10 时,dist是小数
        所以采用ceil函数(也就是以1px为单位) 变化,直到相等*/
        if (lpos < xpos) {
            dist = Math.ceil((xpos - lpos)/10);
            lpos+=dist;
        }
        if (lpos > xpos) {
            dist = Math.ceil((lpos - xpos)/10);
            lpos-=dist;    
        }
        elem.style.left = lpos;
        elem.movevent = setTimeout("movePreview('"+id+"',"+xpos+")",10);
    }
    
</script>
</body>
</html>

 

posted @ 2013-03-15 18:15  mguo  阅读(342)  评论(0编辑  收藏  举报