what does express-async-handler do?

Question

Hey I am trying to comprehend what does express-async-handler do?

It was used in one of the repo I was looking.

From their docs, it says

Simple middleware for handling exceptions inside of async express routes and passing them to your express error handlers.

Link for the repo: https://www.npmjs.com/package/express-async-handler

Can someone please explain this with example?

Answer 1

The example in the npm page shows this:

express.get('/', asyncHandler(async (req, res, next) => {
    const bar = await foo.findAll();
    res.send(bar)
}))

Without asyncHandler you'd need:

express.get('/',(req, res, next) => {
    foo.findAll()
    .then ( bar => {
       res.send(bar)
     } )
    .catch(next); // error passed on to the error handling route
})

or using async/await:

express.get('/', async (req, res, next) => {
    try {
        const bar = await foo.findAll();
        res.send(bar);
    } catch (err) {
        next(err); // error passed on to the error handling route
    }
});

With the library, no catch is needed to call next() if an error is thrown within the route.