js打开新窗口返回值IE正常/firefox失败_sos

测试页面
http://kyouj.com/test/test_111.html
关键代码如下

[code="java"]JScript code
function gopen(url,w,h)//定义打开窗口的返回值
{
var isMSIE= (navigator.appName == "Microsoft Internet Explorer"); //判断浏览器
if (isMSIE){

var selProdWnd = window.showModalDialog(url, window, "dialogWidth="+w+"px;dialogHeight="+h+"px;status:0;scroll:no");
}
else {
var selProdWnd = window.open(url, "mcePopup", "scrollbars=no,dialog=yes,modal=yes,width=500,height=500,resizable=no" );
return false;
}
if (selProdWnd!=undefined)
{
document.getElementById("textfield").value= selProdWnd
//}
}
}
[/code]

它怎么修改才支持firefox呢？？

[code="java"]
function gopen(url,w,h)//定义打开窗口的返回值
{
var isMSIE= (navigator.appName == "Microsoft Internet Explorer"); //判断浏览器
if (isMSIE){

var selProdWnd = window.showModalDialog(url, window, "dialogWidth="+w+"px;dialogHeight="+h+"px;status:0;scroll:no");
if (selProdWnd!=undefined)
{
document.getElementById("textfield").value= selProdWnd;
//}
}
}
else {
var selProdWnd = window.open(url, "mcePopup", "scrollbars=no,dialog=yes,modal=yes,width=500,height=500,resizable=no" );
return false;
}

}

[/code]

[code="java"]
function goback()
{
formval="值测试";
var isMSIE= (navigator.appName == "Microsoft Internet Explorer");
if(isMSIE)
window.returnValue=formval;
else
opener.document.getElementById("textfield").value= formval;
window.close();
}

[/code]