var html = "<p><a href=‘http://www.baidu.com/‘>Ruby Louvre</a>by <em>test</em></p>";
var text = html.replace(/<(?:.|\s)*?>/g, "");
alert(text)

var html = "<p><a href=‘http://www.baidu.com/‘>Ruby Louvre</a></p><hr/><p>by <em>test</em></p>";
var text = html.replace(/<(?!hr)(?:.|\s)*?>/ig,"")
alert(text)//Ruby Louvre<hr/>by test