davo / react-performance

Let's make our apps fast ⚡

React Performance

Let's make our apps fast ⚡

👋 hi there! My name is Kent C. Dodds! This is a workshop repo to teach you about profiling React applications to identify slow parts and using proven tools and techniques to make your app fast.

Pre-Workshop Instructions/Requirements

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

• Setup the project (follow the setup instructions below) (~5 minutes)
• Install and setup Zoom on the computer you will be using (~5 minutes)
• Install the React DevTools (Chrome (recommended), Firefox)
• Watch Use Zoom for KCD Workshops (~8 minutes).
• Watch Setup and Logistics for KCD Workshops (~24 minutes). Please do NOT skip this step.
• Watch The Beginner's Guide to React (available free on Egghead.io), or have the equivalent experience (77 minutes)
• Watch my talk Why React Hooks (35 minutes)
• Go through my Learn React Hooks Workshop, or have the equivalent basic experience of using hooks. You should be experienced with useState, useEffect, and useRef.
• Go through my Advanced React Hooks Workshop, or have the equivalent experience. You should be experienced with useContext and useReducer (experience with useMemo and useCallback is a bonus).

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

Workshop Outline

Here are the tools and techniques we'll be covering:

• Loading less code via code splitting
• Install and explore the React DevTools
• Identify and fix slow components with React DevTools Profiler
• Identify and fix slow JavaScript with the Chrome DevTools Profiler
• Use Web Workers to free up the main thread from expensive computations
• Solve "perf death by a thousand cuts"
• Optimize context providers
• Production Monitoring

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.

Setup

For many of my workshops, you should be able to run them entirely in the browser. However for this one, most of the exercises require you run scripts and do some performance analysis that doesn't work well in that environment. So I recommend you work through the workshop on your own computer.

To do so, please follow these instructions.

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

git clone https://github.com/kentcdodds/react-performance.git
cd react-performance
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.

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)
• Peter the Product Manager 🕴 helps us know what our users want
• Alfred the Alert 🚨 will occasionally show up in the test failures with potential explanations for why the tests are failing.

Troubleshooting

"npm run setup" command not working

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

# verify your environment will work with the project
node ./scripts/verify

# install dependencies
npm install

# verify the project is ready to run
npm run build
npm run test:coverage
npm run lint

# automatically fill in your email for the feedback links.
node ./scripts/autofill-feedback-email.js

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.

Contributors

Thanks goes to these wonderful people (emoji key):

Kent C. Dodds 💻 📖 🚇 ⚠️

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

License

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 [email protected]