碰撞缓冲效果的导航条 js

浏览数：35 / 时间：2015年06月09日

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head>
<title>碰撞缓冲效果的导航条</title>
<style type="text/css">
* { padding: 0; margin: 0; }
li { list-style: none; }
body { background: #fff; }
ul { width: 202px; margin: 40px auto 0; position: relative; }
li { width: 200px; height: 30px; line-height: 30px; padding-left: 10px; border: 1px solid #ccc; border-left: 3px solid #666; font-size: 14px; color: #333; margin-bottom: 5px; position: relative; z-index: 2; }
a { color: #333; text-decoration: none; }
.active { font-weight: bold; background: #fff0f0; }
#bar { width: 10px; padding-left: 0; background: #cc6699; border: 1px solid #cc6699; position: absolute; top: 0; left: -14px; z-index: 3; }
</style>
<script type="text/javascript">
    var obj = null;
    var aLis = null;
    var oBar = null;
    var iTime = null;
    var iSpeed = 0;
    var iAcc = 3;
    var onOff = 0;
    var iPrev = 0;
    var iNext = 0;
    function goTime() {
        for (var i = 0; i < aLis.length; i += 1) {
            if (aLis[i] === this) {
                var iTarget = (aLis[0].offsetHeight + 5) * i;
                iNext = i;
                onOff = iNext - iPrev;
                if (iTime) {
                    clearInterval(iTime);
                }
                if (onOff >= 0) {
                    iTime = setInterval("elasticity(" + iTarget + ")", 35);
                }
                else {
                    iTime = setInterval("postpone(" + iTarget + ")", 35);
                }
                iPrev = iNext;
            }
            aLis[i].className = "";
            this.className = "active";
        }
    }
    function elasticity(target) {
        var top = oBar.offsetTop;
        iSpeed += iAcc;
        top += iSpeed;
        if (top >= target) {
            iSpeed *= -0.7;
            if (Math.abs(iSpeed) <= iAcc) {
                clearInterval(iTime);
                iTime = null;
            }
            top = target;
        }
        oBar.style.top = top + "px";
    }
    function postpone(target) {
        if (oBar.offsetTop === target) {
            clearInterval(iTime);
            iTime = null;
        }
        else {
            iSpeed = (target - oBar.offsetTop) / 4;
            oBar.style.top = oBar.offsetTop + iSpeed + "px";
        }
    }
    window.onload = function () {
        obj = document.getElementById("nav");
        aLis = obj.getElementsByTagName("li");
        oBar = document.getElementById("bar");
        for (var i = 0; i < aLis.length; i += 1) {
            if (aLis[i].id != "bar") {
                aLis[i].onmouseover = goTime;
            }
        }
    };
</script>
</head>
<body>
<ul id="nav">
<li class="active"><a href="#">首页</a></li>
<li><a href="/">烈火学院</a></li>
<li><a href="/">妙味课程</a></li>
<li><a href="/">联系方式</a></li>
<li id="bar"></li>
</ul>
</body>
</html>