I'm building a Node.js / Socket.io project.

I have a Hash of Users based on their websocket id. When a user makes the following request i'd like to add them to a group of users viewing that page.

app.get('/board/:id', function(req, res){}

I'd like to keep something like

Browsing = { Username : id, username : id, ... }

However i'm unsure how to remove a user lets say if they navigate off the page. Is there some kind of function that gets called upon page leave?

Partial Solution:

   $(window).unload(function(){
      var username = $('#username').text();
      var pid = currentProject;

      var data = {
        username: username,
        id : pid
      }

      socket.emit('leaving-page', data);
    })

... Is there some kind of function that gets called upon page leave? ...

Yes, but it is not reliable.

The way the people keep track of who is online and who isn't, is usually like this:

• Add the time when the user last refreshed/visited a page
• set a limit to you consider them offline