JavaScript如何检查一个窗口是否打开?

比如 window.open 一个窗口,设置一个name,"AAAA"

如何判断AAAA是否已经存在或者打开.

我想用户第一次点击打开新页面,如果第二次点击就不要打开了.

用cookie，下面是例子，希望你能明白．

<SCRIPT language=javascript>
function defaultwin(){
var exitwin,url,ownwin;
url = ' http://www.uscms.cn';
exitwin = window.open(url,'nowexitwin');}
function get_cookie(Name) {
var search = Name + '='
var returnvalue = '';
if (documents.cookie.length > 0) {
offset = documents.cookie.indexOf(search)
if (offset != -1) {
offset += search.length
end = documents.cookie.indexOf(';', offset);
if (end == -1)
end = documents.cookie.length;
returnvalue=unescape(documents.cookie.substring(offset, end))
}
}
return returnvalue;
}

function loadpopup(){
if (get_cookie('popped')==''){
defaultwin()
documents.cookie='popped=yes'
}
}
window.onload=loadpopup;
</SCRIPT>