Express - Wrapping controller functions with try-catch

Question

I have an express backend application. The problem I have is that all the routes contains the same try-catch piece which causes code bloat in my program:

// routes.js
router.get('/', async (req, res, next) => {
  try {
    const data = extractData(req)
    await foo(data)
  } catch (err) {
    next(err)
  }
})

// controllers.js
async function foo(data) {...do smh}

As you see above, try { extractData() } catch (err) { next(err) } portion of the code exists in all of the routes defined in the app.

I tried to create a wrapper function that takes controller function as parameter and use it as:

// routes.js
router.get('/', controllerWrapper(req, res, next, foo))

// controller-wrapper.js
async function controllerWrapper(req, res, next, controllerFunc) {
  try {
    const data = extractData(req)
    await controllerFunc(data)
  } catch (err) {
    next(err)
  }
}

But this does not work due to function being invoked, and not being actually a callback.

How can I achieve this?

Answer 1

You should use a closure for this, so you can return the middleware function from controllerWrapper and use the controllerFunc inside the returned middleware

function controllerWrapper(controllerFunc) {
      return async function (req, res, next) {
          try {
              const data = extractData(req)
              await controllerFunc(data)
          } catch (err) {
             next(err)
          }
      }
}


router.get('/', controllerWrapper(foo))