正则表达式答疑

Question

var html = "<p><a href='http://www.cnblogs.com/rubylouvre/'>Ruby Louvre</a>by <em>司徒正美</em></p>";var text = html.replace(/<(?:.|\s)*?>/g, "");console.log(text);//VM247:3 Ruby Louvreby 司徒正美求大神给我讲解下这个正则表达式，实在看不明白π-π。。。谢谢啦