In Express4, how to force a MIME type for negotiation

Question

In Express4, how to force a MIME type for negotiation

In Express 4, what's the best approach to forcing a particular MIME type to be used in a subsequent res.format(...) call?

Content negotiation works perfectly (when using curl and manual headers) but I'm in a browser where I want to force a PDF to be downloaded, so I need to override it on demand. I don't really want to have to make a whole new URL route for the same content (nasty and non-RESTy).

There are still references to req.accepted in the docs (under here: http://expressjs.com/api#req.accepts) but that doesn't seem to exist in the source code. Seems that the changes in Express 4 have changed the API somehow in a way that has slipped through the documentation.

I've tried res.type() and a whole bunch of other things that used to work, but to no avail.

node.js
express
content-negotiation

Answer 1

I have an answer, but I don't much like it. I'm doing the following in my middleware:

knowledgeMiddleware = function(req, res, next) {

  // Allow bypass on content negotiation when the mimeType
  // query parameter is set

  if (req.query.hasOwnProperty('mimeType')) {
    req.headers.accept = req.query.mimeType;
    delete req.query.mimeType;
  }

  ...
  next()
}

Any better ideas?