Proper way to set response status and JSON content in a REST API made with nodejs and express

Question

Express API reference covers this case.

See status and send.

In short, you just have to call the status method before calling json or send:

res.status(500).send({ error: "boo:(" });

You could do it this way:

res.status(400).json(json_response);

This will set the HTTP status code to 400, it works even in express 4.

status of 200 will be the default when using res.send, res.json, etc.

You can set the status like res.status(500).json({ error: 'something is wrong' });

Often I'll do something like...

router.get('/something', function(req, res, next) {
  // Some stuff here
  if(err) {
    res.status(500);
    return next(err);
  }
  // More stuff here
});

Then have my error middleware send the response, and do anything else I need to do when there is an error.

Additionally: res.sendStatus(status) has been added as of version 4.9.0 http://expressjs.com/4x/api.html#res.sendStatus

A list of HTTP Status Codes

The good-practice regarding status response is to, predictably, send the proper HTTP status code depending on the error (4xx for client errors, 5xx for server errors), regarding the actual JSON response there's no "bible" but a good idea could be to send (again) the status and data as 2 different properties of the root object in a successful response (this way you are giving the client the chance to capture the status from the HTTP headers and the payload itself) and a 3rd property explaining the error in a human-understandable way in the case of an error.

Stripe's API behaves similarly in the real world.

i.e.

OK

200, {status: 200, data: [...]}

Error

400, {status: 400, data: null, message: "You must send foo and bar to baz..."}