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> <li>1</li> <li>2</li> <li>3</li> <li>4</li> </ul> </body> </html>