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Advanced React Hooks

👋 hi there! My name is Kent C. Dodds and this is the source material for Advanced React Hooks!

Travis Build Status AppVeyor Build Status GPL-3.0 License All Contributors PRs Welcome Code of Conduct

Pre-Workshop Instructions/Requirements

In order for us to maximize our efforts during the workshop, please do the following:

The more prepared you are for the workshop, the better it will go for you.

Workshop Outline

You will be learning and using the following hooks: useReducer, useContext, useMemo, useCallback, useLayoutEffect, useImperativeHandle, and useDebugValue.

  1. useReducer: simple Counter
  2. useReducer: HTTP requests
  3. useContext: simple Counter (covers useMemo and useCallback as well)
  4. useContext: Caching response data in context (covers useMemo and useCallback as well)
  5. useLayoutEffect: auto-growing textarea
  6. useImperativeHandle: scroll to top/bottom
  7. useDebugValue: useMedia

System Requirements

  • git v2 or greater
  • NodeJS v8 or greater
  • yarn v1 or greater (or npm v6 or greater)

All of these must be available in your PATH. To verify things are set up properly, you can run this:

git --version
node --version
yarn --version # or npm --version

If you have trouble with any of these, learn more about the PATH environment variable and how to fix it here for windows or mac/linux.


You should be able to work through the entire workshop in the browser. This is actually the recommended approach as it requires absolutely no setup whatsoever. Go to this codesandbox and you should be good to go.

Edit advanced-react-hooks

If you'd rather be able to work through the workshop on your own computer, then follow the following instructions.

After you've made sure to have the correct things (and versions) installed, you should be able to just run a few commands to get set up:

# If you were given instructions for a specific branch to use, then use this command
# git clone --single-branch --branch <branchname>

# otherwise, this is fine:
git clone

# then do this:
cd advanced-react-hooks
npm run setup --silent

This may take a few minutes. It will ask you for your email. This is optional and just automatically adds your email to the links in the project to make filling out some forms easier If you get any errors, please read through them and see if you can find out what the problem is. You may also want to look at Troubleshooting. If you can't work it out on your own then please file an issue and provide all the output from the commands you ran (even if it's a lot).

Running the app

To get the app up and running (and really see if it worked), run:

npm start

This should start up your browser. If you're familiar, this is a standard react-scripts application.

You can also open the deployment of the app on Netlify.

Running the tests

npm test

This will start Jest in watch mode. Read the output and play around with it.

Working through it

This a very exercise-heavy workshop. You'll find the exercises in the src/exercises directory. I recommend running the tests and the application. When you start an exercise, pull up the exercises page in the app and the test in the src/__tests__ directory.

Your goal will be to go into each test, swap the final version for the exercise version in the import, and make the tests pass

Helpful Emoji 🐨 💰 💯 🦉 📜 💣 🚨

Each exercise has comments in it to help you get through the exercise. These fun emoji characters are here to help you.

  • Kody the Koala Bear 🐨 will tell you when there's something specific you should do
  • Marty the Money Bag 💰 will give you specific tips (and sometimes code) along the way
  • Hannah the Hundred 💯 will give you extra challenges you can do if you finish the exercises early.
  • Olivia the Owl 🦉 will give you useful tidbits/best practice notes and a link for elaboration and feedback.
  • Dominic the Document 📜 will give you links to useful documentation
  • Berry the Bomb 💣 will be hanging around anywhere you need to blow stuff up (delete code)
  • Alfred the Alert 🚨 may occasionally show up in the test failures with potential explanations for why the tests are failing.


"npm run setup" command not working

Here's what the setup script does. If it fails, try doing each of these things individually yourself:

# install dependencies
npm install

# verify your environment will work with the project
npm run validate

If any of those scripts fail, please try to work out what went wrong by the error message you get. If you still can't work it out, feel free to open an issue with all the output from that script. I will try to help if I can.

"Error: ENOSPC: System limit for number of file watchers reached" when running tests

Try increasing your system's file watchers limit:

echo fs.inotify.max_user_watches=524288 | sudo tee -a /etc/sysctl.conf && sudo sysctl -p

Read more about what’s happening at


Thanks goes to these wonderful people (emoji key):

Kent C. Dodds
Kent C. Dodds

💻 📖 🚇 ⚠️
Frank Calise
Frank Calise


Michael Friedman
Michael Friedman

Brandon Newton
Brandon Newton

📖 💻
Jonathan Bruce
Jonathan Bruce

Łukasz Gandecki
Łukasz Gandecki


This project follows the all-contributors specification. Contributions of any kind welcome!


This material is available for private, non-commercial use under the GPL version 3. If you would like to use this material to conduct your own workshop, please contact me at

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