Update Express tutorial to v5

[hamishwillee]

This updates the Express Tutorial to v5

I wrote some tests in mdn/express-locallibrary-tutorial#327, then updated Express to v5 along with all dependencies - everything passed. Then ran all the code mods (npx @expressjs/codemod upgrade) suggested in the migration guide - nothing was changed. So I don't think I was using anything impacted by a changed or removed API.

I have updated the docs now. Mostly this was removing code to do async error handling in routes using asyncHandler since Express now handles that automatically. Also updated the Express sections on handling errors so this is more clear.
The route path handling is also different, so I had to update that section - it wasn't anything I was using in the demo, but it was significant for readers.

I also updated the database connection to to be done in bin/www since that allows for testing.
The way it was done in the app.js means that tests can't work (because you can't have multiple connections, and if you do this in the app there is already a connection by the time you get to the test runner).

Last of all I went through the lot and checked all the docs and versions of libraries. I did not retest the deployment though (mostly because I did that fairly recently).

Actions:

• Fix up all links from 4x to 5x
• Fix up the mongoose instructions to set up the tests in the bin/www file.
• Fix up later instructions that update the DB url so that they point to www.
• Fix up environment instructions to match current LTS versions of node etc.
• Fix up all dependencies.
• Remove v4 patch for hacking async error handling
• Work through and tidy up docs.
• https://developer.mozilla.org/en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/routes#route_paths - I think this changed. Check in path route matching syntax in https://expressjs.com/en/guide/migrating-5.html#res.send.status

Fixes #38922

[github-actions]

Preview URLs (23 pages)

• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/Displaying_data/Author_detail_page
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/Displaying_data/Author_list_page
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/Displaying_data/BookInstance_detail_page_and_challenge
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/Displaying_data/BookInstance_list_page
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/Displaying_data/Book_detail_page
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/Displaying_data/Book_list_page
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/Displaying_data/Genre_detail_page
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/Displaying_data/Home_page
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/Displaying_data/LocalLibrary_base_template
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/Introduction
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/deployment
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/development_environment
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/forms/Create_BookInstance_form
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/forms/Create_author_form
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/forms/Create_book_form
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/forms/Create_genre_form
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/forms/Delete_author_form
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/forms/Update_Book_form
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/forms
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/mongoose
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/routes
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/skeleton_website
• /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs

External URLs (17)

URL: /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs
Title: Express web framework (Node.js/JavaScript)

• https://mongoosejs.com/ (1 time)
• https://nodejs.org/dist/latest-v10.x/docs/api/ (1 time)
• https://stackoverflow.com/questions/2353818/how-do-i-get-started-with-node-js/5511507 (1 time)
• https://www.quora.com/What-is-the-greatest-resource-for-learning-Node-js-for-a-newbie (1 time)

---

URL: /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/Displaying_data/Home_page
Title: Home page

• https://expressjs.com/en/5x/api.html (1 time) (Note! This may be a new URL 👀)

---

URL: /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/forms/Update_Book_form
Title: Update Book form

• https://mongoosejs.com/docs/api/query.html (1 time) (Note! This may be a new URL 👀)

---

URL: /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/Introduction
Title: Express/Node introduction

• https://expressjs.com/ (2 times) (Note! This may be a new URL 👀)
• https://expressjs.com/en/5x/api.html (10 times) (Note! This may be a new URL 👀)
• https://expressjs.com/en/guide/routing.html (3 times) (Note! This may be a new URL 👀)
• https://nodejs.org/ (1 time) (Note! This may be a new URL 👀)
• https://nodejs.org/api/util.html (1 time) (Note! This may be a new URL 👀)

---

URL: /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/routes
Title: Express Tutorial Part 4: Routes and controllers

• https://expressjs.com/en/5x/api.html (6 times) (Note! This may be a new URL 👀)
• https://expressjs.com/en/guide/error-handling.html (1 time) (Note! This may be a new URL 👀)
• https://expressjs.com/en/guide/routing.html (4 times) (Note! This may be a new URL 👀)
• https://expressjs.com/en/starter/basic-routing.html (2 times) (Note! This may be a new URL 👀)

---

URL: /en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/skeleton_website
Title: Express Tutorial Part 2: Creating a skeleton website

• https://expressjs.com/en/5x/api.html (1 time) (Note! This may be a new URL 👀)
• https://pugjs.org/api/getting-started.html (2 times) (Note! This may be a new URL 👀)

(comment last updated: 2025-07-16 08:07:12)

[chrisdavidmills]

@hamishwillee sterling work, sir. I've read through all the changes and made a few suggestions, but nothing major.

A couple of questions:

• Do you need me to run through it all and make sure it all works, or have you already done this with confidence? I'm assuming you have, but happy to help with this if not.
• I've not checked in detail whether you've missed any instances of mass replaced terms such as 4x -> 5x, but I'm assuming you've grepped for these?

[chrisdavidmills]

why do we need a jade dependency if it is now called pug?

[hamishwillee]

Good catch. I will fix

[github-actions]

This pull request has merge conflicts that must be resolved before it can be merged.

[hamishwillee]

@chrisdavidmills - I have accepted all your changes, a couple with minor mods. Thanks so much.

Do you need me to run through it all and make sure it all works, or have you already done this with confidence? I'm assuming you have, but happy to help with this if not.

I don't think this is necessary - though the offer appreciated!

For the bits where code changes, mostly this was just removal of the asyncHandler which is no longer needed. I have retested those bits match the demo code for the "final version". I haven't run through every step from scratch - e.g., starting from the original empty handlers that we build on, but this was more or less a search and replace so I'm not concerned.

I've not checked in detail whether you've missed any instances of mass replaced terms such as 4x -> 5x, but I'm assuming you've grepped for these?

Yes it was a grep.

Upshot, I am pretty confident of this. Should be good to go. mdn/express-locallibrary-tutorial#327 should merge at a similar time.

[chrisdavidmills]

@hamishwillee woo hoo — awesome work!

I'm approving this, but I won't merge it. I'll let you do that once the other related PR is ready to go too.

[hamishwillee]

Thanks @chrisdavidmills . It's all good!