In your case you need to add this...
[( /<i class[\s\S]*?>[\s\S]*?<\/i>/gi ),( /<span class[\s\S]*?>[\s\S]*?<\/span>/gi ),( /<em class[\s\S]*?>[\s\S]*?<\/em>/gi ),( /<button class[\s\S]*?>[\s\S]*?<\/button>/gi ),( /<a class[\s\S]*?>[\s\S]*?<\/a>/gi )]