Node.js Express handle errors function

Question

In express app, I researched that we can handle error using something like this:

// app.js
app.use(function (error, req, res, next) {
    // Handle errors
});

my questions are:

am I right that this function will be called only if there is an error? I could not get this function to call if there is no error. Am I missing anything?
is there any case that this function will get called even there is no error?

Thanks

Nitzan Shaked · Accepted Answer · 2013-09-13 05:56:19Z

2

Yes. Middleware with arity of 4 (that is: err, req, res, next) are error handlers, and will be called when there's an error.

Errors may be uncaught exceptions in your other middleware, or explicitly errors that you raise when you call next(err) instead of next() with no arguments.

There will be cases when these handlers won't be called. For example: errors that happen in async blocks.

answered Sep 13, 2013 at 5:56

Nitzan Shaked

13.6k5 gold badges48 silver badges55 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Nam Nguyen Over a year ago

very useful info and quick reply. Appreciated @Nitzan Shaked. +1

Collectives™ on Stack Overflow

Node.js Express handle errors function

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related