一、多物体运动
需要注意：每个运动物体的定时器作为物体的属性独立出来互不影响，属性与运动对象绑定，不能公用；
例子1：
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>多物体运动</title>
<style>
div{ width:100px; height:100px; background:red; float:left; margin:10px; border:1px solid black; opacity:0.3; filter:alpha(opacity=30);}
</style>
<script>
window.onload = function()
{
var aDiv = document.getElementsByTagName('div');
aDiv[0].onmouseover = function()
{
startMove(this, 'width', 300);
};
aDiv[0].onmouseout = function()
{
startMove(this, 'width', 100);
};
aDiv[1].onmouseover = function()
{
startMove(this, 'height', 300);
};
aDiv[1].onmouseout = function()
{
startMove(this, 'height', 100);
};
aDiv[2].onmouseover = function()
{
startMove(this, 'opacity', 100);
};
aDiv[2].onmouseout = function()
{
startMove(this, 'opacity', 30);
};
aDiv[3].onmouseover = function()
{
startMove(this, 'borderWidth', 20);
};
aDiv[3].onmouseout = function()
{
startMove(this, 'borderWidth', 1);
};
};
function getStyle(obj, attr)
{
if(obj.currentStyle){
return obj.currentStyle[attr];
}else{
return getComputedStyle(obj, false)[attr];
}
}
function startMove(obj, attr, iTarget)
{
clearInterval(obj.timer);
obj.timer = setInterval(function(){
var iCur = 0;
if(attr == 'opacity'){
iCur = parseInt(parseFloat(getStyle(obj, attr)) * 100);
}else{
iCur = parseInt(getStyle(obj, attr));
}
var iSpeed = (iTarget - iCur) / 8;
iSpeed = iSpeed > 0 ? Math.ceil(iSpeed) : Math.floor(iSpeed);
if(iCur == iTarget){
clearInterval(obj.timer);
}else{
if(attr == 'opacity'){
obj.style.filter = 'alpha(opacity='+ (iCur+iSpeed) +')';
obj.style.opacity = (iCur+iSpeed)/100;
}else{
obj.style[attr] = iCur + iSpeed + 'px';
}
}
}, 30);
}
</script>
</head>
<body>
<div></div>
<div></div>
<div></div>
<div></div>
</body>
</html>