代碼精簡的可以實現元素圓角的js函數

上次在blueidea上看到一個元素圓角的實現方法，但是那個太複雜了。於是就自己寫了一個函數，可以將元素自動圓角。
示範地址：http://longbill.cn/down/sample/roundcorner.htm
不要用在有 padding 值得元素上，最好是在外面套一層。詳情見示範地址。
代碼：
function RoundCorner(obj,style)
{
/********
網頁元素圓角函數!!
作者: Longbill
首頁: www.longbill.cn
********/
var r = [];
var styles = [
{top:["0 5px","0 3px","0 2px","0 1px","0 1px"],bottom:["0 1px","0 1px","0 2px","0 3px","0 5px"]},
{top:["0 5px","0 3px","0 2px","0 1px","0 1px"],bottom:["0px","0px","0px","0px","0px"] },
{top:["0 0 0 5px","0 0 0 3px","0 0 0 2px","0 0 0 1px","0 0 0 1px"],bottom:["0 1 0 0px","0 1 0 0px","0 2 0 0px","0 3 0 0px","0 5 0 0px"]},
{top:["0 5 0 0px","0 3 0 0px","0 2 0 0px","0 1 0 0px","0 1 0 0px"],bottom:["0 0 0 1px","0 0 0 1px","0 0 0 2px","0 0 0 3px","0 0 0 5px"]}
]; //author: longbill.cn
if (!style || style>styles.length) style = 1;
style--;
var btop = styles[style].top,bbottom = styles[style].bottom;
obj = document.getElementById(obj);
if (!obj) return;
var HTML = obj.innerHTML;
obj.innerHTML = "";
for(var istop=1;istop>=0;istop--)
{
var topborder = document.createElement("b");
topborder.style.display = "block";
topborder.style.height = "2px";
topborder.style.backgroundColor = (obj.parentNode.style.backgroundColor)?obj.parentNode.style.backgroundColor:"#FFFFFF";
for(var i=0;i<btop.length;i++)
{
var b = document.createElement("b");
if (obj.style.backgroundColor)
b.style.backgroundColor = obj.style.backgroundColor;
else if (obj.className)
b.className = obj.className;
b.style.display = "block";
b.style.margin = (istop)?btop[i]:bbottom[i];
b.style.height = "1px";
b.style.overflow = "hidden";
b.style.width = "auto";
topborder.appendChild(b);
}
obj.appendChild(topborder);
if (istop) obj.innerHTML+=HTML;
}
}