var user1 = "Frank"; // UID of user 1 var user2 = "Eusthace"; // UID of user 2
var roomName = 'chat_'+(user1<user2 ? user1+''+user2 : user2+''+user1);
console.log(user1+', '+user2+' => '+ roomName);
user1 = "Eusthace"; user2 = "Frank";
var roomName = 'chat_'+(user1<user2 ? user1+''+user2 : user2+''+user1);
console.log(user1+', '+user2+' => '+ roomName);
var roomName = 'chat_'+(user1<user2 ? user1+''+user2 : user2+''+user1);
could be translated to
var roomName = 'chat${user1.compareTo(user2) < 0 ? '$user1$user2' : '$user2$user1'}';
It could be that I am wrong with the <... If yes, > is correct. :-)
Okay, short explanation: x.compareTo(y) is a sorting method on many classes (including String). It returns -1 if x should be sorted before y, +1 if it should be sorted after y, and 0 if both are usually ranked equally.
Strings are sorted alphabetically (not sure about special characters like German umlauts though), DateTime objects are sorted as "earlier before later", and so on. In your own classes, you are free to define your own sorting logic (and it makes sense to also use a compareTo method for it).