Middleware factory pattern in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a middleware factory that returns a middleware function.

Express

function logger(level) {
  return function(req, res, next) {
    console.log(level + ': Request received');
    [1]();
  };
}

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

Ares

Bnext

Creq

Dconsole

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to call next() causes the request to hang.

The middleware factory returns a function that calls next() to pass control to the next middleware.

2fill in blank

medium

Complete the code to use the middleware factory with a specific log level.

Express

const express = require('express');
const app = express();

app.use(logger([1]));

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

A'info'

Binfo

Clevel

Dconsole

Attempts:

3 left

💡 Hint

Common Mistakes

Passing an undefined variable instead of a string.

The log level should be passed as a string to the middleware factory.

3fill in blank

hard

Fix the error in the middleware factory to correctly handle the next function.

Express

function logger(level) {
  return function(req, res, next) {
    console.log(level + ': Request received');
    [1];
  };
}

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

Anext

Bnext.call

Cnext.call()

Dnext()

Attempts:

3 left

💡 Hint

Common Mistakes

Writing next without parentheses, causing the middleware to not proceed.

The next function must be called with parentheses to invoke it.

4fill in blank

hard

Fill both blanks to create a middleware factory that logs the method and URL of requests.

Express

function requestLogger([1]) {
  return function(req, res, [2]) {
    console.log(req.method + ' ' + req.url);
    next();
  };
}

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

Alevel

Bnext

Cres

Drequest

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong parameter names or forgetting to call next().

The factory takes a parameter level and the middleware function uses next to continue.

5fill in blank

hard

Fill all three blanks to create a middleware factory that adds a custom header with the given name and value.

Express

function headerSetter([1], [2]) {
  return function(req, res, [3]) {
    res.setHeader([1], [2]);
    next();
  };
}

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

AheaderName

BheaderValue

Cnext

Dres

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing parameter names or forgetting to call next().

The factory takes headerName and headerValue. The middleware function uses next to continue.