如何使用快速中间件充当API响应者？

Question

My route definition is:

app.put '/api/v1/user/oldest', userController.oldestAndUpdate, responder

in userController , I have:

exports.oldestAndUpdate = (req, res, next) ->
  doSomeStuff, (err, results) ->
    return next err if err
    req.apiResponse = results
    next()

in my responder , I have:

module.exports = (req, res, next) ->
  response = req.apiResponse
  response.status = 'ok'

  res.json response

But how do I handle the error case? If the next(err) is hit, how will my responder know there's an error?

Answer 1

If there is ever an error passed to next , the middleware chain and routing is stopped, and it skips straight to the error handling middleware.

The error handling middleware is special, as it has four arguments: err, req, res, next. Internally, express checks the arity (number of arguments) of every middleware handler, and if it has 4 it's used as the error handler. From here you can respond in the same style as the rest of your API.

There is an example error handler in the expressjs guide .