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JavaScript Build a REST API With Express Completing and Testing the API Connecting the API and Database

PoJung Chen
PoJung Chen
5,856 Points
Posted by PoJung Chen
PoJung Chen
5,856 Points

There is no 'err' parameters in `router.param('aID', callback)`

In the lecture, there is a code write like below:

router.param('aID', function (req, res, next, id) {

  req.answer = req.question.answers.id(id)   if (!req.answer) {
    err = new Error('Not Found')
    err.status = 404
    return next(err)
  }
  next()
})

However, there is no err parameter in the callback function. Is there anything I mistype?

Tom Geraghty
Tom Geraghty
24,174 Points
Tom Geraghty
Tom Geraghty
24,174 Points

It might be more clear if, in the video, it was written like this: 

var err = new Error('Not Found');

So people don't think the value is being passed in from elsewhere rather than being created in that instance (i.e.: when there is no req.answer).

1 Answer

Gerry K
Gerry K
5,877 Points
Gerry K
Gerry K
5,877 Points

Hi,

The error is being created at:

err = new Error('Not Found')
err.status = 404
return next(err)

And the last line above is passing the error off to the Error Handler.

You would only be passing the err into a callback function into the error handler to let Node know that its the error handler.

If you look in the app.js file it has the error handler code which I've pasted below:

app.use(function(err, req, res, next){
    res.status(err.status || 500);
    res.json({
        error: {
            message: err.message
        }
    });
});