关于用JS处理字符串的问题

Question

<script  type="text/javascript" >
var a='http://forum.csdn.net/PointForum/Forum/PostTopic.aspx'
alert(a.replace(/[^\/]*?\/[^\/]*?\/[^\/]*?\/(.*?)/,"$1"))
</script>

Answer 1

<script  type="text/javascript" >
var a='http://forum.csdn.net/PointForum/Forum/PostTopic.aspx'
alert(a.replace(/^[^\/]*?\/[^\/]*?\/[^\/]*?\/(.*?)$/,"$1"))
</script>

Answer 2

var   a='http://forum.csdn.net/PointForum/Forum/PostTopic.aspx' 
a.replace(/http://([\s\S]?![/])*/,"");

Answer 3

var str = 'http://forum.csdn.net/PointForum/Forum/PostTopic.aspx';
alert(str.replace(/(?:[^\/]*\/){3}(.*)/g, function($0, $1){return $1.replace(/\//g, '%20');}));

Answer 4

如果是页面的URL用 
  encodeURICompanent(location.pathname)