This course gets you up and running with react in under a minute by using codesandbox.io to skip the painful process of setting up your dev environment.

Chris Achard

React Crash Course with Hooks

In this course, we’ll create an online/offline note-taking app.  We’ll use `create-react-app` to create the frontend, and node.js to create a simple backend. 

Progressive Web Apps in React with create-react-app

We’ll build a mobile app with React Native for both iOS and Android. Prior React experience is required, but you don’t have to know mobile development to participate.

Build a React Native Application for iOS and Android from Start to Finish

In this collection, you'll create a simple game with React using Recoil, to explore how you can share and update state across an app.

Getting Started with Recoil in React

Chris Achard Landing Page

 Courses from Chris Achard

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

There are two methods to append strings together in javascript, but there are edge cases that you have to watch out with each of them.

First, you can use the `+` operator to add strings together:

```
"first" + " " + "second"
```

which works, but watch out!  If one of your variables is a non-string value, then it will try to convert that to a string before adding it to the other string.

The other method is to use the `concat` method:

```
"first".concat(" ", "second")
```

but `concat` has a big problem because now if the first value is a non-string value (like `null` or `undefined`), then it will cause a runtime error, since the `concat` method is undefined on those values.

For that reason, most people use the `+` operator to add two strings together in javascript.

Append two strings together in javascript (with edge cases)

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

Instead of just returning a value from a recoil selector, you can return any promise, which means that you can do asynchronous functions in recoil selectors (this is a little like a redux thunk).

The huge bonus is that you don't have to do anything different when actually calling the selector - use can use `useRecoilValue` in the same way that you would from a normal selector.

The only thing you must do is somewhere in the component tree, wrap any component that uses an async selector with a `<React.Suspense>` tag with a `fallback` prop that will tell React what to display when the async selector isn't loaded yet.





Use Async Functions in a Recoil Selector

Recoil is a new (experimental!) library from facebook that can handle complex shared data across a large react app.

In this collection, we'll create a simple game with React using Recoil, to explore how you can share and update state across an app. 

Recoil is similar to (but different than) Context, Redux, or other shared state libraries (like MobX), but is designed to handle large (and variable) numbers of state that can update without re-rendering your entire app's component tree.

A state management library for React.

Recoil works and thinks like React. Add some to your app and get fast and flexible shared state.

recoil

To change a value in state we can do that directly (by pulling the atom with `useRecoildState`), or we can write a custom hook that will change the value for us:

```
const useResetScore = () => {
  const [score, setScore] = useRecoilState(gameScore)
  return () => {
    setScore(0)
  }
}
```

That function returns a function that we can then call from a component like any other hook:

```
  const resetScore = useResetScore()
```

and then we can use that new `resetScore` function for the `onClick` of a button:

```
<button onClick={resetScore}>Reset</button>
```

which will change the value in the Recoil state.

That's a simplistic example of a custom hook - but that hook could then be extended to do multiple state changes, and then could be imported into any component in the React tree and used.

Write a Custom Recoil Hook to Reset a Value in the Recoil State

To compute a value from one or more values stored in Recoil, we can create a "selector".

First import `selector` from Recoil, and then call it with an object that has two keys: `key` and `get`:

```
import { selector } from recoil;
...
const paperSize = selector({
  key: 'paperSize',
  get: ({get}) => {
    const score = get(gameScore)
    return 100 + (score * 5)
  }
})
```

Inside of the `get` function we can get the current value of the `gameScore` atom from recoil, and then compute a new value from that to return to our game.  Then we can get the value using `useRecoilValue`:

```
import { paperSize } from './selectors'
...
const size = useRecoilValue(paperSize)
```


Compute a Value in Recoil Using a Selector

To get a value from Recoil we can import the atom that we want and the hook `useRecoilValue` from recoil.

Then we can get the value:

```
import { useRecoilValue } from 'recoil'
...
import { gameScore } from './atoms'
...
const score = useRecoilValue(gameScore)
```

And display it in a lablel:

```
<h3>Score: {score}</h3>
```

That value will update every time the button is clicked (and `setScore` is called) automatically!

Read a Value from Recoil with useRecoilValue

We'll create a new bit of shared state (called an "atom" in Recoil) by importing `atom` from Recoil and setting a unique key and default value:

```
import {
  atom
} from 'recoil'

const gameScore = atom({
  key: 'gameScore',
  default: 0
})
```

Then we can use that `gameScore` by calling the Recoil hook `useRecoilState`

```
import {
  useRecoilState
} from 'recoil'

...

  const [score, setScore] = useRecoilState(gameScore)
```

That looks a lot like a local `useState` call - but is different because it creates the state in Recoil, which can then be used in this component, or in any other component in the tree (underneath the same `RecoilRoot`)

Create Shared State with Recoil in a React App

We'll create a new React game with:

```
npx create-react-app paper-game
cd paper-game
```

and then install Recoil with:

```
npm install recoil
```

and start the server:

```
npm start
```

Then, to wrap the entire app in the recoil root, we'll import `RecoilRoot` from `recoil` and wrap the app:

```
    <RecoilRoot>
      <Game />
    </RecoilRoot>
```

And the app is now up and running - ready to use Recoil



Set Up Recoil in a new React App

Get started with React! (with Hooks)

This course gets you up and running with react in **under a minute** by using codesandbox.io to skip the painful process of setting up your dev environment. 

You'll learn:

- How to write React code with JSX
- How to "think in React"
- How to use local state to store changing data
- How to pass data from parent components to children components using props

So get started now!  You need some javascript and HTML experience, but no prior React experience is needed.

**🚨 The correct url is now "https://swapi.dev/api/people/"**

Whenever doing a side effect (like fetching data) in React, we can use the `useEffect` hook to perform that action and then set state afterwards.

So we'll fetch some data inside of useEffect like this:

```
  useEffect(() => {
    console.log(props.id)
    fetch("https://swapi.co/api/people/"+props.id)
      .then(response => response.json())
      .then(result => setData(result))
  }, [props.id])
```

Caution! make sure to set the dependency array (the second argument to useEffect) to contain any data that you use inside of the `useEffect`.  Otherwise you could end up with an infinite loop as the useEffect will run every time the component in re-rendered.



Perform Asynchronous Actions (like fetching http data) in React with useEffect

There are two main (default) ways to add styles to React components:

First, just normal CSS classes can be added to react components by setting a `className` attribute:

```
<p className='big-text'>BIG</p>
```

(It's called `className` instead of `class` because "class" is a reserved keyword in javascript)

Second, "inline styles can be added as javascript objects to the `style` attribute of a component:

```
<p style={{ fontSize: 20, color: 'blue' }}>Blue</p>
```

Notice that the "double curly braces" represent a javascript object being created _inside_ of JSX, and also that the css attributes are camel cased.

Adding Styles to React Components with CSS or Inline Styles

To display a list of items in react, we can `map` (or loop) over that list and return JSX from inside the map function:

```
    <div>
      {
        props.items.map(item => {
          return <p key={item.id}>{item.title}</p>
        })
      }
    </div>
```

Remember to always include a `key` attribute though! That lets React keep track of each list item internally, which gives you better performance, and may save you from subtle bugs

Display a List in React by Looping Over an Array of Items

After creating some state with `useState`, we can call the set function to update the data in local state, which will automatically "re-render" the component, and update the UI.

To do that, we'll first create a new function that will update the state that we want:

```
const updateCount = () => {
  setCount(count + 1)
}
```

and then we can pass that `updateCount` function into the `onClick` of a button:

```
<button onClick={updateCount}>Click Me!</button>
```

which will then call `updateCount` once clicked, which will call `setCount`, which will update the `count` state, and automatically display that update on the UI.

Create a Button in React that Changes Local State and Automatically Updates the UI

Data inside of a react component that can change (with user or server interaction) is called `state`.

import `useState` from react, and then we can use that function to create some local state by calling it with a default value:

```
const [count, setCount] = useState(5)
```

`useState` returns an array of two items: the first is the current value of the state, and the second is a function that we can use to update that state.

Create State Data that can Change in a React Component with useState

To pass data from a parent react component to a child react component, we can supply "attributes" to the JSX tags like:

```
<Greeting name="React" />
```

That `name` attribute is then available in the `Greeting` component as a `prop` (which is an object passed in as the first argument to the react function component.

That means we can display that name from the `props` argument like this:

```
function Greeting(props) {
  return(<p>{props.name}</p>)
}
```

And so you can customize any react component by passing data down in the form of that props argument.

Reusing Custom React Components by Passing Data Down as Props

You can reuse your custom react components multiple times and build them into a tree of components like this:

```
<Greeting />
<div>
  <Greeting />
</div>
```

Notice that the `<div>` tag contains the `Greeting` tag as a child, but the `Greeting` tag contains no children - so it requires the trailing slash (`/>`) so it can be a "self closing" tag

Building a Tree of UI Components in React with Children or with Self-closing tags

React components are functions that return JSX (which looks like HTML, but is actually a flavor of javascript).

Once you create a new function component that returns JSX, you can then use it from inside of another component by returning it like any other component.

Write a Custom Function Component in React with JSX

Every UI on the web can be thought of as a tree of "components".

Break down your UI in your mind by separating out "like" components.  Those are what you'll turn into React components for displaying your data.

Think in React by Breaking Your UI into Components

The React UI loop follows these steps:

1. You have data
2. That data gets displayed
3. The data updates (by user input, or a fetch from the server, etc)
4. The UI updates

The React "magic" is in step 4 - React automatically updates the UI based on your changing data in a performant way.  That means you can focus on your data and UI layout, and NOT on how you would have to update the DOM to show those changes.

How React Works

Go to codesandbox.io and start a new sandbox using the "React" template

Then, you can edit the HTML (which is actually a special form of javascript called JSX) to make your first custom component!

CodeSandbox is great because it skips the need to set up your on development environment - so you can get started super quickly.

Write Your First React Component with CodeSandbox.io

Git is a free and open source distributed version control system designed to handle everything from small to very large projects with speed and efficiency.

If you want to pull over just a single commit from one branch onto another, you can do that with `git cherry-pick [HASH-TO-MOVE]`

We'll demonstrate that by making a commit on a feature branch, and then copying that commit (but not the entire branch) onto master.

Copy a Commit from One Branch to Another

Stop waiting for a single AI agent! This lesson demonstrates a powerful workflow to massively parallelize your AI-driven development in Cursor. Learn how to use tools like `file-forge` to package your project context, prompt advanced AI models (like Gemini in AI Studio) to brainstorm features and generate setup scripts, and then leverage a custom `git worktree` CLI tool (`wt`) to automatically launch an "army" of isolated Cursor instances, each tackling a different task on its own branch.

**Workflow Demonstrated / Key Benefits:**

*   **Bundle Project Context:** Use `file-forge` to create an AI-friendly representation of your codebase.
*   **AI-Powered Brainstorming & Scripting:** Prompt a reasoning model (e.g., Gemini via AI Studio) to suggest features *and* generate a shell script (`zsh`/`bash`) to automate setup.
*   **Automated Worktree Creation:** Execute the generated script which uses a custom `git worktree` CLI (`wt`) to:
    *   Create new branches and worktrees for each suggested feature.
    *   Install dependencies automatically (e.g., `pnpm install`).
    *   Launch multiple, isolated Cursor instances.
*   **Parallel AI Development:** Assign different features or implementation approaches to each Cursor agent (Composer) simultaneously.
*   **Efficient Monitoring:** Easily switch between active Cursor projects/worktrees using `Ctrl+R` or OS spaces.
*   **Seamless Integration:** Merge completed features back into your main branch using `wt merge` or use agents to commit, push, and create Pull Requests via the GitHub CLI (`gh pr create`).
*   **Boost Productivity:** Dramatically speed up iteration and experimentation by running multiple AI agents concurrently without conflicts.

This approach transforms your workflow, allowing you to explore multiple development paths simultaneously and integrate the best results efficiently using standard Git practices.

**Resources** 

https://www.npmjs.com/package/@johnlindquist/worktree
https://www.npmjs.com/package/@johnlindquist/file-forge

**Want to Learn More? Sign-up for my Cursor Workshop!**

https://egghead.io/workshop/cursor

John Lindquist

Swarm Intelligence: Massively Parallelize Your AI Agents in Cursor

Creating powerful and context-aware tools for Cursor IDE becomes straightforward when leveraging information directly from your current project. In this lesson, you'll learn how to build a custom MCP (model context protocol) tool that intelligently requests essential details—such as the current project path and conversation summaries—from your Cursor project.

Workflow demonstrated in this lesson:

- Define MCP tool parameters to request specific project details.
- Pass project path and conversation summaries into your MCP tool.
- Automatically write or update files within your current project using these parameters.

Key benefits:

- Automate tasks with precision based on your active project's context.
- Simplify interactions by creating AI-driven CLI commands tailored to your needs.
- Open endless possibilities for integrating external APIs and advanced automation.

Through this practical demonstration, you'll gain a versatile technique for enhancing your development workflow in Cursor IDE.

[https://github.com/johnlindquist/mcp-cursor-tool-starter](https://github.com/johnlindquist/mcp-cursor-tool-starter)

Build MCP Tools Using Project Context for Custom Cursor IDE Automation

Setting up custom MCP (Machine Command Protocol) servers in Cursor can involve tedious steps, such as configuring node paths or referencing additional commands. This lesson shows how to streamline this process by bundling your MCP server directly into a standalone executable.

Workflow demonstrated in this lesson:

- Use a simple MCP server project starter.
- Run a single bundling command to create an executable.
- Right-click the generated executable, copy its full path, and add that directly to your Cursor settings.

Key benefits:

- Eliminates the need for complex node path configurations.
- Simplifies the setup and integration of custom MCP servers into Cursor.
- Makes the server executable instantly accessible within your Cursor environment.

By following this streamlined approach, you can quickly and easily integrate custom MCP servers into Cursor, making your development workflow cleaner and more efficient.

[https://github.com/johnlindquist/mcp-cursor-tool-starter]()

Easy MCP Server Setup in Cursor IDE with Bundled Executables

TanStack Router is the foundation for TanStack Start, which is gaining significant attention due to its innovative approach to application development.

This course focuses on getting effective TanStack Router, a modern and scalable routing solution for React applications. You will learn how to:
- set up and scaffold new applications,
- use file-based routing
- create nested routes
- manage dynamic route parameters and more.

The course covers advanced features like route loaders, caching strategies, and lifecycle hooks, which are crucial for enhancing application performance and user experience.

By understanding TanStack Router, you can build more efficient, type-safe, and maintainable applications, leveraging its integration with data fetching libraries like TanStack Query.

This knowledge is essential for developers looking to improve their routing skills and stay ahead in the field.

Tomasz Ducin

Up and Running with Tanstack Router and React

Learn TanStack Router for React: set up apps, use file-based routing, manage routes, and boost app performance.


In this lesson, we explore how TanStack Router integrates with the [native browser history API](https://developer.mozilla.org/en-US/docs/Web/API/History) to manage navigation.

As we navigate through different routes, the URL changes are stored in the browser's history, allowing users to use the forward and backward buttons to traverse their navigation history.

This functionality also **enables permalinks**, meaning users can copy and paste URLs to access specific routes directly.

Additionally, we learn how to programmatically interact with the history object to move forward or backward through the navigation stack, enhancing the user experience by providing full control over navigation actions.

This compatibility with the native history API ensures that TanStack Router applications behave similarly to traditional websites, offering a seamless and intuitive user experience.

Browse History in Tanstack Router

Browse history in TanStack React Router using the native history API for seamless navigation

In this lesson, we explore how to hook into TanStack Router's lifecycle hooks to execute custom logic during route changes.

The hooks we'll look into are: `onEnter`, `onStay`, and `onLeave`, which are triggered when entering, staying within, or leaving a route, respectively.

All hooks receive a detailed match parameter, providing information about the route's path, ID, and tons of other details.

This allows for the implementation of features like animations or logging when navigating between routes.

We also learn how to use these hooks to track and manage state changes as users interact with the application, making it easier to implement complex behaviors based on route transitions.

Hook into Route Lifecycle Hooks in Tanstack Router

Hook into TanStack React Router's lifecycle hooks for custom route logic and animations.

In this lesson, we learn how to handle not found errors in TanStack Router by using the `notFoundComponent` at both nested and global levels.

To trigger the display of a `notFoundComponent`, we must throw a specific error using the `notFound` function within a loader or other lifecycle method of a route. This approach allows us to provide custom error messages for specific routes or globally across the application.

We explore how to define a notFoundComponent within a specific route's configuration and how to set a `defaultNotFoundComponent` at the router global level, which applies to all routes unless overridden locally. This flexibility ensures that users receive meaningful feedback when encountering non-existent routes.

Provide NotFoundComponent at Nested Route or Global Level in Tanstack Router

Handle notFound errors in TanStack Router with notFoundComponent at nested or global levels.



In this lesson, we learn how to access dynamic route parameters using the `useParams` hook in TanStack Router.

When used with a specific `Route` object, `useParams` provides type-safe access to route parameters, ensuring that TypeScript knows the exact types of these parameters.

This approach eliminates the possibility of undefined/optional values, making it safer for accessing parameters like `employeeId`.

However, when using `useParams` globally without specifying a route, it requires an options object with `{ strict: false }`, which reduces type safety.

In this case, the hook can access parameters from any route in the application, but it does not guarantee their existence or type. This flexibility allows components to be reused across different routes, but it requires careful handling of potential errors.



Access Dynamic Route Parameters with useParams in Tanstack Router

Access dynamic route parameters with useParams in TanStack React Router for type-safe routing.

In this lesson, we learn how to reorganize file-based routes in TanStack Router to accommodate nested routing structures.

We explore how to create additional nested routes by converting files into directories, allowing for further nesting.

For example, to create a nested route like `/employees/$employeeId/edit`, we can create a **directory** (!) named `$employeeId` and place an `index.tsx` file inside it to define the route component for this nested route.

This approach provides flexibility in organizing files while maintaining the convention that file names and locations align with route paths. We also see how to adapt existing components and loaders to work with these reorganized routes, enabling features like edit forms or delete actions (or whatever) within nested routes.


Reorganize File-Based Routes in Tanstack Router

Reorganize file-based routes in TanStack Router for flexible nested routing.



In this lesson, we learn how to parametrize the loader for a nested route in TanStack Router.

We focus on a nested route like `/employees/$employeeId`, where the `$employeeId` is a **dynamic parameter**.

To fetch data for this route, we use a `loader` function that accesses the `$employeeId` parameter. This is achieved by using the params object available in the `loader` function, which contains the dynamic segments of the URL. We then use this parameter to call a function like `getEmployeeById`, which fetches specific employee details from an API.

We highlights that TanStack Router **automatically infers types** for these parameters, ensuring type safety for nested routes.

Parametrize Route Loader for Nested Route in Tanstack Router

Parametrize nested route loaders in TanStack Router using path parameters

Chris Achard

React Crash Course with Hooks

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