用js实现同一页面多个不同运动效果

效果如下，每一个的运动效果都不一样哟~~

要点一：

function getstyle(obj,name){
if(obj.currentStyle){
return obj.currentStyle[name];
}else{
return getComputedStyle(obj,false)[name];
}
}

从样式表中根据id和属性名取值。

要点二：

if(attr == "opacity"){
cur = Math.round(parseFloat(getstyle(obj,attr))*100);
}else{
cur = parseInt(getstyle(obj,attr));
}

如果设置的是透明度的值，因为有可能会是小数点，所以需要用parseFloat，然后有可能会有小数，用round方法四舍五入取整。

如果设置的非透明度值，用parseInt，可以只取数值部分

其它的注意点，前面几篇都有提到，此处不再赘述。

最后，上代码

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>无标题文档</title>
<style>
body,ul,li{margin:0; padding:0;}
#runs li{width:80px; height:80px; background:#06c; list-style:none; margin:10px; border:1px solid #000; filter:alpha(opacity=30); opacity:0.3;}
</style>
<script>
window.onload = function(){
  var runs = document.getElementById("runs");
  var runs_li = runs.getElementsByTagName("li");
    runs_li[0].onmouseover = function(){
      startrun(this,"width",300);
    }
    runs_li[0].onmouseout = function(){
      startrun(this,"width",80);
    }
    runs_li[1].onmouseover = function(){
      startrun(this,"height",300);
    }
    runs_li[1].onmouseout = function(){
      startrun(this,"height",80);
    }
    runs_li[2].onmouseover = function(){
      startrun(this,"fontSize",50);
    }
    runs_li[2].onmouseout = function(){
      startrun(this,"fontSize",14);
    }
    runs_li[3].onmouseover = function(){
      startrun(this,"opacity",100);
    }
    runs_li[3].onmouseout = function(){
      startrun(this,"opacity",30);
    }
}

function startrun(obj,attr,target){
  clearInterval(obj.timer);
  obj.timer = setInterval(function(){
  var cur = 0;
  if(attr == "opacity"){
    cur = Math.round(parseFloat(getstyle(obj,attr))*100);
  }else{
    cur = parseInt(getstyle(obj,attr));
  }
  var speed = (target - cur)/8;
  speed = speed>0?Math.ceil(speed):Math.floor(speed);
    
    if(cur == target){
      clearInterval(obj.timer);
    }else{
      if(attr == "opacity"){
        obj.style.filter='alpha(opacity='+(cur+speed)+')';
        obj.style.opacity=(cur+speed)/100;
      }else{
        obj.style[attr] = cur+speed+"px";
      }
    }
    
  },30);
}

function getstyle(obj,name){
  if(obj.currentStyle){
    return obj.currentStyle[name];
  }else{
    return getComputedStyle(obj,false)[name];
  }
}
</script>
</head>

<body>

<ul id="runs">
  <li style="top:0">1</li>
  <li style="top:90px;">2</li>
  <li style="top:180px;">3</li>
  <li style="top:270px;">4</li>
</ul>
</body>
</html>