[css+js] 富有弹性碰撞缓冲的竖向导航条

2014-08-18 23:47:03 -0400

代码复制

<style type="text/css"> 
* { padding: 0; margin: 0; }
li { list-style: none; }
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> 
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="/">网站首页</a></li>
	<li><a href="#">关于我们</a></li>
	<li><a href="#">资源下载</a></li>
	<li><a href="#">联系方式</a></li>
    <li id="bar"></li>
</ul>

代码说明

富有弹性碰撞缓冲的竖向JavaScript导航条，当鼠标由上往下滑动时，小块跟着往下掉，是一种反弹的碰撞运动；当鼠标由下往上滑动时，小块跟着往上爬，是一种缓冲运动。同时高亮显示当前菜单。

代码演示

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