Express Utils

A simple library with some utils to use with Express. Below is a short summary of the features, but more information can be found in the code/tests.

Main features:

HttpError

A subclass of the native JavaScript Error. Can be used to add a status code and additional info to an Error. The HttpError meant to be used in conjunction with the HttpError.Handler() middleware.

HttpError.Handler()

Will construct an Express ErrorRequest Handler that handles HttpErrors thrown in a request.

wrapMiddleware(handler: Express.Handler, ignoreReturnValue?: boolean)

Can be used to wrap Express Handlers, will catch async errors (rejected promises) and will feed them back into the Express next to be handled by the regular ErrorRequest Handlers.

By default this function will also send any returned (non-null) object with a status 200 as json. Of course only if no response has already been sent and iff ignoreReturnValue is not true.

Example:

// The `wrapMiddleware` function will catch the HttpError 
// and forward it to the `Handler`
app.get(wrapMiddleware(async (req, res) => {
    // Business as usual in an Express Handler...
    // ...

    // And at some point..
    // The `HttpError.Handler()` below will catch this and return:
    // `res.status(418).json({ error: 'What am I?' });`
    throw new HttpError(418, `What am I?`);
}));

app.get(wrapMiddleware(async(req, res) => {
    // By default returned objects will be sent as
    // `res.status(200).json({ some: 'thing' });`
    return { some: 'thing' };
}));

// This will handle all the thrown `HttpError`s
app.use(HttpError.Handler());

Disclaimer

This is mainly used by me and projects I work on. There could be big issues with the implementation or documentation I haven't noticed because I simply don't use it that way.

So use at your own risk and if some feature or documentation is missing/faulty/etc.: PR's are welcome!