The easiest way is to split string using forward slash
var firstString = url.split('/')[1];
and you will have first string, but if you want to extract using regext than this will do, just remember don't add global parameter in your regex.
/([a-zA-Z0-9]{0,})
I hope this helps
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…