Express 3.x error handler

app.coffee

express = require 'express'
error_handler = require './lib/error_handler'
 
module.exports = app = express() 
 
app.configure () ->
  app.use(express.bodyParser()) # standard express http stack
  app.use(app.router)
  app.use(error_handler) # attach error handler
 
app.listen(process.env.PORT or 3000) # start server
console.log "Express server listening on port #{process.env.PORT or 3000} in #{app.settings.env} mode"

error_handler.coffee

# handle errors that are propogated from route
logger = require './logger'
emailer = require './emailer'

module.exports = (err, req, res, next) ->
  if not err then return next() # continue if no error
  
  logger.error err.stack # log the stack (if you want)
  
  # send an email to the developers to let them know an error happened and they need to fix it
  email = {}
  email.message = err.stack.replace(new RegExp('\n', 'gi'), '<br/>')
  emailer.send(email) # no callback, emailer holds default 'to', 'from', 'subject' fields
  
  res.jerror(err) # send the user the error