I tried it... But don't think I did it right since it crashes when I get invited. I definitely need more practice!
client.on('groupRelationship', function(steamID, relationship) {
if(relationship === Steam.EClanRelationship.Invited) {
client.respondToGroupInvite(accept, true);
console.log("Joined Group " + steamID.getSteam3RenderedID() + "!");
}
});
(Accidentally posted in wrong thread I was reading)