 Courses from Michel Weststrate

React is one of the web’s most popular frameworks for building JavaScript applications. 

If you know what you’re doing, React can drastically simplify how you build, use, and maintain code.

Whether you’re a React newbie or you’re ready for advanced techniques, you can level-up with egghead. Explore our in-depth courses, lessons, and community resources to build more powerful applications and crack open your career.

react

The UI we’ve build in the previous lessons works fine. But, we can make it way more efficient and we will use the React profiler to analyse our app.

Since parts of the state tree that haven’t changed compared to the previous state, are shared, we can optimize. This lesson uses the “memo” and “useCallback”  functions from React to benefit from structural sharing.

Profile React Rendering and Optimize with memo to Leverage Structural Sharing

JavaScript® (often shortened to JS) is a lightweight, interpreted, object-oriented language with first-class functions, most known as the scripting language for Web pages, but used in many non-browser environments as well such as node.js or Apache CouchDB. It is a prototype-based, multi-paradigm scripting language that is dynamic, and supports object-oriented, imperative, and functional programming styles.

javascript

Once we’ve written a bunch of producer functions, we quickly discover a recurring pattern: In practice producers can be defined purely in terms of the draft (and any remaining arguments). Therefor we can factor out the function nesting by leveraging currying. We will also look at the “original” function.

Simplify Immer Producer Functions using Currying

In the immutable data paradigm, it is quite important that we don’t accidentally change the data somewhere. It would break the paradigm in ways that are very hard to debug. In this lesson we’ll discover how Immer can help us by automatically freezing all data that is produced.

Furthermore, when writing reducers by hand it is quite easy to accidentally create new state trees, where this wasn’t needed. We will discover how Immer avoids this problem.

Produces Immutable Data and Avoid Unnecessary Creation of New Data Trees with Immer

Occasionally, you might want to write a producer that doesn’t change the draft, but rather returns a completely new data set. This can be achieved by using the return keyword.

Return Completely New State from an Immer Producer

Sometimes our update logic is asynchronous. In this lesson we will investigate two ways in which we can write asynchronous update logic. 

…But, we will also discuss why asynchronous producers should be avoided, and how that can be done by better separating our logic. 

This lesson also demonstrates the “createDraft” and “finishDraft” APIs

Write Asynchronous Producers in Immer and Why You Shouldn’t

When using immutable data as state representation; update logic is often captured in reducers. In this lesson we will take our existing logic, and express it using a typical reducer.

Update Immutable State with React useReducer through Immer

Since Immer records the changes we are trying to apply to our state, it can produce JSON patches. They describe the minimal difference between two versions of the state. This lesson introduces the “produceWithPatches” API.

Capture Patches to Distribute Changes in App State with Immer produceWithPatches

In this lesson we will send patches over a WebSocket to our server, and distribute them again from there.

Create a Simple WebSocket Server to Distribute Patches from Immer

Continuing on the previous lesson, in this one we will make sure that clients can receive patches, and apply them to their local state so that we get real time synchronization. This lesson introduces the “applyPatches” API.

Apply Patches using Immer applyPatches to Synchronize State across Clients

Our naive synchronization implementation has some flaws. In this lesson we are going to address one of them, by changing our index-based storage to key based storage, which enables us to better deal with synchronization issues. 

Create Stable Patches in Immer by updating with Id instead of Indices

Many cool things can be done with immutable data and patches. In this lesson we will highlight one fun trick: Compressing patches by replaying and re-recording them so that we end up with the least amount of patches to end up in the correct final state.

Compress the Immer Patch History by Replaying Patches on a setInterval

In our last lesson we will add another big feature, undo that works even when multiple users are present. We will build undo by using inverse patches, that are like patches, but can be used to replay from the next state to the previous state.

Use Immer inversePatches to Build Undo Functionality

In this lesson we will capture our undo history with a stack and a pointer, so that we will able to implement redo as well.

Use Immer Patches to Build Redo Functionality

Using immutable data to store state has many interesting benefits. Immutable data makes it easy to trace state over time. It can be distributed easily, and by leveraging structural sharing we can leverage optimization techniques such as memoization.

In this course we will build a multi user gift-list, in which we will discover how using immer doesn’t just significantly simplifies our state manipulation code. It also provides us with very useful tools such as patches that can help us to distribute changes, build undo/ redo, etc.

Introduction to the in-depth Immer course

Our core logic of the Gifts application is written using pure functions, that produce an entirely new, immutable state. This allows us to reap the benefits of immutability in the remainder of the course.

Capture Application Logic in Pure Functions to Create Immutable State

Our “app” now stores it state using immutable values. However, that wasn’t easy. Luckily Immer can help us to write logic in way more straight-forward ways, without loosing any of the benefits of immutability. We will introduce the concepts “produce”, “draft” and “recipe”

Simplify Deep State Updates using Immer produce

It is time to create a simple front-end for our application. As example, we will use React in this course to render our data. We will use setState to store our application’s state, and hook the event handlers up to the logic we wrote before.

Render Immutable Data using React

The great thing about having producers outside components is that it is becomes very straightforward to test them independent of our UI logic.

However, in some cases your logic might be so simple that you want to use Immer inside some of your react components. In this lesson we will discover how. For example by using “useImmer” or “useImmerReducer” from the use-immer package.

Immutable Update State inside React components with useImmer

A small caveat with Immer is that arrow functions that consist of just an expression, and not a function block, always return a value.

In this lesson we will show that in these cases the `void` keyword can be used to avoid accidentally returning new state in addition to modifying the draft.

Avoid Accidental Returns of New State by using the void Keyword

Because the code put in recipe functions is plain, native, mutable JavaScript code, Immer is naturally suited to be used in conjunction of TypeScript (or Flow). 

In this lesson we will discover how to combine Immer with TypeScript, and how to type our data types both with simple types and with readonly types.

Type Immutable Immer Data with TypeScript

Using immutable data structures provides many benefits, including making your code easier to reason about and less prone to bugs.

However, since JavaScript doesn't include support for immutable data structures out of the box, you need to use a third party library. But which one to choose?

In this self-paced workshop, Immer's creator Michel Westrate will guide you through the creation of a multi-user Gift Tracking app.

You'll learn the basics of using Immer to handle immutable state updates, then go further into change distribution and implementing an undo/redo.

After this workshop, you'll be ready to leverage immutable data structures in your own applications!

Immutable JavaScript Data Structures with Immer

When comparing two visually similar websites, it can often be challenging to precisely identify the subtle differences between them. To facilitate a rapid analysis of these discrepancies, a practical technique involves leveraging Chrome's integrated developer tools to capture full-page screenshots of each site. Subsequently, these screenshots can be uploaded to a platform like AI Studio. There, the AI can analyze the images and generate a report detailing the variations. This entire process, leveraging a few quick shortcuts, can be completed in under a minute, delivering a comprehensive breakdown of the differences for efficient comparison and analysis.

Quickly Compare Two Sites Using AI Studio with Chrome Full Page Screenshots

It's fairly trivial to create a React project, but there's always a big hurdle between creating it locally and making it shareable so that someone else can run it. This lesson walks you through the process of automating creating a React project locally, creating the repository where it's going to be hosted, and creating shareable links where it can be run so that you can quickly and easily create single one-off demos and shoot them over to your friends and coworkers for sharing your code ideas in a working environment.


```bash
share-react-project() {
  if [[ -z "$1" ]]; then
    echo "Usage: share-react-project <project_name>"
    return 1
  fi

  local project_name="$1"
  local github_username=$(gh api /user --jq '.login')

  echo "Creating Vite project: $project_name"
  pnpm create vite "$project_name" --template react

  cd "$project_name"

  echo "Initializing Git repository"
  git init

  echo "Adding all files to Git"
  git add .

  echo "Creating initial commit"
  git commit -m "Initial commit"

  local codesandbox_link="https://codesandbox.io/p/github/${github_username}/${project_name}"

  echo "Adding CodeSandbox link to README.md"
  echo "" >> README.md
  echo "## CodeSandbox" >> README.md
  echo "[![Open in CodeSandbox](https://assets.codesandbox.io/github/button-edit-blue.svg)](${codesandbox_link})" >> README.md

  echo "Adding README.md to Git"
  git add README.md

  echo "Committing README.md changes"
  git commit -m "Add CodeSandbox link"

  echo "Creating GitHub repository: $github_username/$project_name"
  gh repo create "$github_username/$project_name" --public

  echo "Pushing to remote 'origin'"
  git push -u origin main

  echo "Project '$project_name' created successfully!"
  echo "GitHub repository: https://github.com/$github_username/$project_name"
  echo "CodeSandbox link: $codesandbox_link"
}
```

Automate Creating a Local React Project, GitHub Repository, and Live Hosted Demo in a Single Command

[Verdaccio](https://verdaccio.org/) is a fully featured NPM registry that you can run locally on your machine. It’s a great tool for testing your release process, running end-to-end tests, and simulating real-world scenarios like deploying packages, installing them, and verifying functionality as an end user would.

Nx includes a [generator](https://nx.dev/features/generate-code) that simplifies setting up Verdaccio. To configure it, run:

```shell
npx nx g @nx/js:setup-verdaccio   
```

This command installs the necessary NPM packages and creates a `project.json` file with a `local-registry` target. To start the local registry, open a new terminal window and run:

```shell
npx nx local-registry
```

This will:
- Launch the Verdaccio registry.
- Configure NPM to point to the local Verdaccio server at `http://localhost:4873`.

> **Note:** A `project.json` file provides an advanced way to define scripts, offering more flexibility than a traditional `package.json` for managing complex targets.

Setup local Verdaccio server to release NPM packages

Learn how to spin up a local NPM registry powered by Verdaccio to test deploy your NPM packages.

In TypeScript, developers often begin by defining the structure of their data using type definitions or interfaces, which is a powerful way to ensure type safety. However, as applications grow and become more complex, simply defining the shape of an object might not be enough to guarantee its consistent creation and behavior throughout the codebase. This often leads to situations where objects that are intended to be of a certain "type" might be missing crucial properties or have incorrect data, which can be difficult to track down and debug.

This lesson tackles the question of when and why to move beyond basic type definitions and embrace classes in TypeScript. It demonstrates how classes provide a more robust mechanism for defining object structure, enforcing type constraints, and ensuring consistent object creation. By establishing a clear blueprint for objects, classes not only improve compile-time type safety but also offer runtime benefits and better code organization, ultimately helping developers avoid common pitfalls associated with loosely structured objects in larger TypeScript projects.

Stop Avoiding Classes in TypeScript

Karabiner isn't only for your keyboard. It can also hijack your mouse buttons and enable them to be similar to layers on your keyboard, where holding down a mouse button can allow you to tap keys on your keyboard to trigger commands and macros that can completely revolutionize your workflows. For example, you can hold down the right mouse button and tap on R to go to references in VS Code. Or hold down the right mouse button and tap the left mouse button to chop up videos and Screenflow.

This completely unlocks a whole new world of possibilities and use cases for your mouse as you can hover your mouse over anywhere on the page. And just tapping keys on your keyboard allows you to trigger mouse actions, to trigger keyboard actions, or to trigger macros and applications and terminal commands. and anything that your imagination can come up with. 

Karabiner: Rethinking Right-Click as a Macro Command Center

Make an HTML table more readable on mobile devices by using the ::before pseudo-element. We add labels to each cell, so they appear like cards when the table is viewed on smaller screens. The ::before content is set using a data-label attribute for each cell to enhance mobile viewability without horizontal scrolling.



Create a mobile friendly table with the before pseudo-element

Learn to use CSS ::before pseudo-element for mobile-friendly HTML tables. Add labels to cells for enhanced readability on mobile, avoiding horizontal scroll.

Any app of a decent size has event flows and messages being passed around. At a certain point it becomes complicated to explain it through prose and you want to turn towards diagrams. Now setting aside the time to create diagrams that accurately describe what's happening in your codebase can be quite time consuming. Luckily, with today's AI tools, we can now just do basic walkthroughs with rough recordings over codebase dictating what's going on along the way and then upload that to tools like AI Studio and then ask it to generate diagrams in a text-based format such as Mermaid that will then generate the flowcharts and diagrams for us. So this video walks us through this process of recording a rough video, uploading it to AI Studio and then asking AI Studio to generate the proper Mermaid diagram syntax.

Generate Mermaid Flow Chart Diagrams with Gemini 2.0 from Rough Screen Recordings

I'm a diehard Karabiner user and anytime I start doing something repetitively I always move it into my Karabiner configuration. Sometimes I'll fall into scenarios where I want to trigger a command, but I also want to know if that command succeeded or failed. Since Karabiner can trigger any command, setting up the command is fairly straightforward, but knowing whether it succeeded or failed became much more difficult. Luckily for me there is a package called terminal-notifier that you can install from homebrew and you can pipe the output of your command to terminal-notifier. And have a seamless way of triggering your keyboard shortcut which runs a command and you can be notified of the results.

Use Karabiner to Trigger a Terminal Command and Get Notified of the Results

There are a lot of scenarios when inspecting a site in Chrome where you don't want any click events to fire and you don't want any scripts to run. Or maybe something is animating in and out of the page and you want to capture it at a certain moment. This is a great use case for pausing script execution, which is kind of using the debugger manually by going into the Chrome DevTools and the Sources tab and clicking the pause button to essentially pause the entire page. This will give you a chance to inspect any of the elements and styles you want to inspect. And you don't have to worry about fire and click events or anything that might interrupt your investigation into the elements and styles that you want to find.

Pause Script Execution in Chrome to Easily Inspect Elements

Gemini 2.0 has a context window of a million tokens, and this means that you can upload hundreds of files and allow it to inspect and analyze massive refactors across entire code bases. 

This lesson demonstrates concatenating an entire code base into a single file and then uploading it to AI Studio. Once within AI Studio, we ask it to find the types of tasks that it can evaluate for us. Then we select one of the tasks and ask it to generate instructions for that task. Once those instructions are complete, we then turn them over to Windsurf's Cascade agent, and we allow Windsurf's Cascade to do all of the work for us as we sit back, relax, and let the AI do our jobs.

Michel Weststrate

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