A Coffeescript Message Wall With Long Poll Properties in Node.JS and Express

wall.coffee

# our application server
app = require('express').createServer()
app.msgs = []   # a history of posted messages
app.defers = [] # a list of deferred responses 

# / redirects to /q
app.get '/', (req, res) => 
    res.redirect('/q')

# /q[/<xxx>] query messages from the wall; may block for a protracted period
app.get '/q/:ofs?', (req, res) =>
    ofs = parseInt(req.params.ofs) || 0
    req.contentType 'text/plain'
    if app.msgs.length > ofs
        # send all messages on the wall to the user, starting from ofs
        res.send app.msgs.slice(ofs).join('')
    else
        # waiting for the future; defer until it arrives
        app.defers.push [ofs, res] 

# /p?msg=<xxx> post a message to the wall
app.get '/p', (req, res) => 
    return if not req.query.msg
    msg = req.query.msg + '\n'
    app.msgs.push(msg)
    
    # the future has arrived, notify all those who have deferred
    defer.send msg for defer in app.defers
    
    # now purge the deferrals
    app.defers = []

# listen to port 3000 for traffic.
app.listen( 3000 )

This is a straight port of my JavaScript wall to CoffeeScript; see https://gist.github.com/192d8b5e0f00a900cf88