JavaScript多物体独立运动实现原理与代码示例

<!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>