I am making a chatroom that uses ajax in javascript to update and send messages. I was wondering if it was possible to do something like this -
If a chat message was sent (chat.send), then make everyone else in the chatroom do a chat update (chat.update).
I'm not sure where to start on this.
Chatroom in the browser? Well it sounds like you are exploring your options so why not look at socket.io? link to socket io chat example. Socket io makes two way communication between the server and client browser possible (provides an interface for sockets), which means you can chat in real time with others, and it works quite intiutively.
Otherwise, if you want to use Ajax, you can use polling. Other users will poll for updates (ask the server for status updates at time intervals) and if one of the users made a chat message they'll receive the chat message while polling from the server.