怎么用正则表达式取得地址的域名

[aqjill]

比如：http://www.zh28.com/news/20060213.html
这个字符串只截取http://www.zh28.com,其它的部分不要 .com、.cn等等都是这样

[hbhbhbhbhb1021]

<script language=javascript>
var str="http://www.zh28.com/news/20060213.html"
re=/(http:\/\/[^\/]+)/
re.test(str)
alert(RegExp.$1)
</script>

[jinjuduo]

<script language=javascript>
var str="http://www.zh28.com/news/20060213.html"
re=/^(http\://[a-z0-9\-\.]+\.[a-z]{2,3})(/\S*)?$/gi;
re.test(str)
alert(RegExp.$1)
</script>

[jinjuduo]

<script language=javascript>
var str="http://www.zh28.com/news/20060213.html";
re=/(^http:\/\/[a-z0-9\-\.]+\.[a-z]{2,3})(\/\S*)?$/gi;
re.test(str);
alert(RegExp.$1);
</script>

[Sing-Z]

这个更简单
<script language=javascript>
var str="http://www.zh28.com/news/20060213.html";
re=/(^http:\/\/[^\/]*)?/gi;
re.test(str);
alert(RegExp.$1);
</script>

[bigman_lfj]

把天外水火的改造了一下，呵呵，追加了.com,.cn制限

<script language=javascript>
var str="http://www.zh28.cn/news/20060213.html"
re=/(http:\/\/[^\/]+(.com|.cn))/
re.test(str)
alert(RegExp.$1)
</script>

[adverse]

<script language=javascript>
var str="http://community.csdn.net/Expert/topic/5430/5430887.xml?temp=.443722";
re=/(^http:\/\/[a-z0-9\-\.]+\.[a-z]{2,3})(\/\S*)?(\?[a-z0-9]=[a-z0-9%])?(&[a-z0-9]=[a-z0-9%])*$/gi;
re.test(str);
alert(RegExp.$1);
</script>