Async middleware wrapper in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create an async middleware wrapper function.

Express

const asyncWrapper = (fn) => (req, res, next) => {
  Promise.resolve(fn(req, res, next)).[1](next);
};

Drag options to blanks, or click blank then click option'

Aresolve

Bthen

Cfinally

Dcatch

Attempts:

3 left

💡 Hint

Common Mistakes

Using then instead of catch causes errors to be unhandled.

Using finally does not pass errors to next.

Using resolve is incorrect as it's not a Promise method.

The catch method is used to handle errors in the async function and pass them to next for Express error handling.

2fill in blank

medium

Complete the code to use the async middleware wrapper with an async route handler.

Express

app.get('/data', [1](async (req, res) => {
  const data = await fetchData();
  res.json(data);
}));

Drag options to blanks, or click blank then click option'

AasyncHandler

BexpressAsyncHandler

CasyncWrapper

DwrapAsync

Attempts:

3 left

💡 Hint

Common Mistakes

Using undefined wrapper function names.

Not wrapping the async function causes unhandled errors.

The asyncWrapper function wraps the async route handler to catch errors and pass them to Express.

3fill in blank

hard

Fix the error in the async middleware wrapper to correctly handle errors.

Express

const asyncWrapper = (fn) => (req, res, next) => {
  fn(req, res, next).[1](next);
};

Drag options to blanks, or click blank then click option'

Acatch

Bthen

Cfinally

Dresolve

Attempts:

3 left

💡 Hint

Common Mistakes

Using then instead of catch.

Not handling errors causes unhandled Promise rejections.

Directly calling fn(req, res, next) returns a Promise, so catch is needed to handle errors and pass them to next.

4fill in blank

hard

Fill both blanks to create an async middleware wrapper that returns a function with correct parameters.

Express

const asyncWrapper = ([1]) => ([2]) => {
  return Promise.resolve([1](...[2])).catch(next);
};

Drag options to blanks, or click blank then click option'

Afn

Breq, res, next

C[req, res, next]

Dargs

Attempts:

3 left

💡 Hint

Common Mistakes

Using parameter names instead of an array for spreading.

Not spreading the arguments causes errors.

The wrapper takes a function fn and returns a function that takes args (an array of parameters). It calls fn(...args) and catches errors.

5fill in blank

hard

Fill all three blanks to create a reusable async middleware wrapper with error forwarding.

Express

function asyncWrapper([1]) {
  return function [2](req, res, next) {
    [3](fn(req, res, next)).catch(next);
  };
}

Drag options to blanks, or click blank then click option'

Afn

Bmiddleware

CPromise.resolve

DasyncWrapper

Attempts:

3 left

💡 Hint

Common Mistakes

Not wrapping the function call in Promise.resolve.

Using incorrect function names.

Not passing errors to next.

The function asyncWrapper takes fn, returns a function named middleware that calls Promise.resolve(fn(req, res, next)) and catches errors to pass to next.