Learn Auth0, Ethereum and Xstate

An easy to implement, adaptable authentication and authorization platform which basically makes your login box awesome.



auth0

After a user successfully logs in, Auth0 sends an ID token to your React application. Auth0, uses ID Tokens to cache user profile information and give it to a client application. The caching of ID tokens can improve the performance and responsiveness of your React application.

You can use the data from the ID token to personalize the user interface of your application. The Auth0 React SDK decodes the ID token and stores its data in the user object from the `useAuth0()` React hook. 

Customize UI With ID Token Data From The useAuth0 Hook's User Object

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

You can log out users from your React application by logging them out of their Auth0 sessions using the `logout()` method from the Auth0 React SDK.

Create a `logout-button.js` file in the src/components/buttons folder

Create a logout button component with the following code

```js
import { useAuth0 } from "@auth0/auth0-react";
import React from "react";

export const LogoutButton = () => {
  const { logout } = useAuth0();

  const handleLogout = () => {
    logout({
      logoutParams: {
        returnTo: window.location.origin,
      },
    });
  };

  return (
    <button className="button__logout" onClick={handleLogout}>
      Log Out
    </button>
  );
};
```

The `logout() method from Auth0 React SDK clears the application session and redirects to the Auth0 /v2/logout endpoint to clear the Auth0 session.

You can pass an object argument to `logout()` to customize the logout behavior of the React application. You can define a `logoutParams` property on that object to define parameters for the /v2/logout call. This process is invisible to the user. 

Pass the `logoutParams.returnTo` option to specify the URL where Auth0 should redirect your users after they log out. 

Setting `logoutParams.returnTo` to `window.location.origin` will ensure that Auth0 redirects your users to your production URL that you add to the "Allowed Logout URLs" list.




End Auth0 User Session with the logout Method from useAuth0 Hook

In this lesson, we create an AuthenticationGuard file that uses the Auth0React SDK to protect React routes by requiring login. 

You need to create the AuthenticationGuard component, pass in a component prop, and use it to protect any React route. 

```js
import { withAuthenticationRequired } from "@auth0/auth0-react";
import React from "react";
import { PageLoader } from "./page-loader";

export const AuthenticationGuard = ({ component }) => {
  const Component = withAuthenticationRequired(component);

  return <Component />;
};
```

Will also demonstrates how to use the AuthenticationGuard component to protect the profile, and admin routes in the application. 

```js
import { useAuth0 } from "@auth0/auth0-react";
import React from "react";
import { Route, Routes } from "react-router-dom";
import { PageLoader } from "./components/page-loader";
import { AuthenticationGuard } from "./components/authentication-guard";
import { AdminPage } from "./pages/admin-page";
import { CallbackPage } from "./pages/callback-page";
import { HomePage } from "./pages/home-page";
import { NotFoundPage } from "./pages/not-found-page";
import { ProfilePage } from "./pages/profile-page";
import { ProtectedPage } from "./pages/protected-page";
import { PublicPage } from "./pages/public-page";

export const App = () => {

  return (
    <Routes>
      <Route path="/" element={<HomePage />} />
      <Route
        path="/profile"
        element={<AuthenticationGuard component={ProfilePage} />}
      />
      <Route path="/public" element={<PublicPage />} />
      <Route
        path="/protected"
        element={<AuthenticationGuard component={ProtectedPage} />}
      />
      <Route
        path="/admin"
        element={<AuthenticationGuard component={AdminPage} />}
      />
      <Route path="/callback" element={<CallbackPage />} />
      <Route path="*" element={<NotFoundPage />} />
    </Routes>
  );
};

```

Use Auth0 component withAuthenticationRequired To Protect React Router 6 Routes

The `isAuthenticated` value represents the authentication state of your users it's tracked by the Auth0 React SDK. This value returns `true` when the user has been authenticated and `false` they're when not. Use `isAuthenticated` to render UI elements conditionally depending on the authentication state of your users.

```js
import { useAuth0 } from "@auth0/auth0-react";
import React from "react";
import { LoginButton } from "../../buttons/login-button";
import { LogoutButton } from "../../buttons/logout-button";
import { SignupButton } from "../../buttons/signup-button";

export const NavBarButtons = () => {
  const { isAuthenticated } = useAuth0();

  return (
    <div className="nav-bar__buttons">
      {!isAuthenticated && (
        <>
          <SignupButton />
          <LoginButton />
        </>
      )}
      {isAuthenticated && (
        <>
          <LogoutButton />
        </>
      )}
    </div>
  );
};
```
Authentication process doesn’t happen in your React application when using Auth0. Your React application will redirect your users to the Auth0 Universal Login page. Auth0 asks for credentials and redirects the user back to your application with the result of the authentication.


Use the Value of isAuthenticated to Render Components Conditionality

Create a `signup-button.js` file under the src/components/buttons folder

Add the following code:

```js
import { useAuth0 } from "@auth0/auth0-react";
import React from "react";

export const SignupButton = () => {
  const { loginWithRedirect } = useAuth0();

  const handleSignUp = async () => {
    await loginWithRedirect({
      appState: {
        returnTo: "/profile",
      },
      authorizationParams: {
        screen_hint: "signup",
      },
    });
  };

  return (
    <button className="button__sign-up" onClick={handleSignUp}>
      Sign Up
    </button>
  );
};
```
Adding `authorizationParams` to the `loginWithRedirect()` configuration object with the `screen_hint ` property and a value of `signup` will take users from your React application to the sign-up page.

Pass authorizationParams to loginWithRedirect to Direct Users to Auth0 Sign Up

Create a buttons folder the src/components folder

Create a `login-button.js` file and add the following code:

```js
import { useAuth0 } from "@auth0/auth0-react";
import React from "react";

export const LoginButton = () => {
  const { loginWithRedirect } = useAuth0();

  const handleLogin = async () => {
    await loginWithRedirect({
      appState: {
        returnTo: "/profile",
      },
    });
  };

  return (
    <button className="button__login" onClick={handleLogin}>
      Log In
    </button>
  );
};
```

`loginWithRedirect()` redirects to the Auth0 /authorize endpoint to start the authentication process. You can pass a configuration object to this method to customize the login experience.

Setting up the value of `appState.returnTo` to "/profile", you are telling the Auth0 React SDK to: When my users log in with Auth0 and return to my React application, take them to the "Profile" page.

If you don't set up this `appState.returnTo` option, your users will be redirected by default to the / path after they log in.

Apply useAuth0 hook and loginWithReditect to Add User Login to React Application

Install the Auth React SDK on the terminal 

```bash
npm install @auth0/auth0-react
```

Create an `auth0-provider-with-navigate.js` file in the src folder.

Add the following code.

```js
import { Auth0Provider } from "@auth0/auth0-react";
import React from "react";
import { useNavigate } from "react-router-dom";

export const Auth0ProviderWithNavigate = ({ children }) => {
  const navigate = useNavigate();

  const domain = process.env.REACT_APP_AUTH0_DOMAIN;
  const clientId = process.env.REACT_APP_AUTH0_CLIENT_ID;
  const redirectUri = process.env.REACT_APP_AUTH0_CALLBACK_URL;

  const onRedirectCallback = (appState) => {
    navigate(appState?.returnTo || window.location.pathname);
  };

  if (!(domain && clientId && redirectUri)) {
    return null;
  }

  return (
    <Auth0Provider
      domain={domain}
      clientId={clientId}
      authorizationParams={{
        redirect_uri: redirectUri,
      }}
      onRedirectCallback={onRedirectCallback}
    >
      {children}
    </Auth0Provider>
  );
};
```

Wrap the `Auth0ProviderWithNavigate` component around the `App` component inside of `index.js` to give it access to the `Auth0Context`.

`Auth0ProviderWithNavigate` needs the `BrowserRouter` component from React Router to be its parent, grandparent, or great-great-great-grandparent.


Install Auth0 React SDK and Create Auth0Provider with Access to Session History

Click the **Create Application** button.

Sign up for a [free Auth0 account](https://a0.to/egghead-react) here. 

Add the name "React Code Sample" and select "Single Page Applications" and the application type then click **Create**

Click on the **Settings** tab of your Auth0 Application page, scroll down to "Application URIs" section, and fill in these values:

**Allowed Callback URLs**
http://localhost:4040/

**Allowed Logout URLs**
http://localhost:4040

**Allowed Web Origins**
http://localhost:4040

Scroll down and click the **Save Changes** button.

On the "Basic Information" section get the Auth0 Domain and Auth0 Client ID values and paste them a `.env` file in the root of the project.

```env
REACT_APP_AUTH0_DOMAIN=AUTH0-DOMAIN
REACT_APP_AUTH0_CLIENT_ID=AUTH0-CLIENT-ID
REACT_APP_AUTH0_CALLBACK_URL=http://localhost:4040/
```





Link Auth0 Application to React Application

Start by cloning the `spa_react_javascript_hello-world_react-router-6` repository on its starter branch:

```bash
git clone -b starter git@github.com:auth0-developer-hub/spa_react_javascript_hello-world.git
```

Change your current directory to `spa_react_javascript_hello-world_react-router-6`

```bash
cd spa_react_javascript_hello-world
```

Install the project dependencies

```bash
npm install
```

Run the React application on `http://localhost:4040`

```bash
npm start
```


Download Starter Application from Auth0 Developer Center

Node.js is a platform built on Chrome's JavaScript runtime for easily building fast, scalable network applications. Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient, perfect for data-intensive real-time applications that run across distributed devices.

node

You can use the post-login Action to redirect users before an authentication transaction is complete. This lets you implement custom authentication flows that require additional user interaction beyond the standard login form.

Call `api.redirect.sendUserTo()` with the URL you want to redirect to as a string

After the redirect, in your app resume authentication by redirecting the user to the `/continue` endpoint and include the `state` parameter from the URL. 

If you don't send the original state back to the `/continue` endpoint, Auth0 will lose the context of the login transaction and the user will not be able to log in.


In your application redirect to: `https://{yourAuth0Domain}/continue?state=abc123`

After the user has been redirected to the `/continue` endpoint, the Action will resume by calling the `onContinuePostLogin` function. 

For redirects to work properly, you must have a uncomment the `onContinuePostLogin` function even if the function is empty.

Check if the user has seen the announcement 

```js
  if (!event.user.app_metadata[''announcement_seen'']) {
    api.redirect.sendUserTo("http:://localhost:3000/announcement");
  }
};
```

If the user hasn't seen the announcement set the `app_metadata`

```js
exports.onContinuePostLogin = async (event, api) => {
  api.user.setAppMetadata('announcement_seen', true);
};
``` 


Redirect User After Login with Auth0 Actions

Add the `slack-notify` npm package from the Actions editor to send a Slack message when a new user registers for your application. 

Create a Post User Registration action.

Go to `api.slack.com` create a new app, active **Incoming Webhooks**, and get your Slack Webhook URL.

> Your webhook URL contains a secret. Don't share it online, including public Git repositories.

In the Action editor store the Slack Webhook URL as a secret and add the `slack-notify` npm package.

In the Actions editor enter the follow code:

```js
const initSlackNotify = require('slack-notify')

exports.onExecutePostUserRegistration = async (event) => {
  const slack = initSlackNotify(event.secrets.SLACK_WEBHOOK_URL);
  const message = `New User: ${event.user.email}`

  slack.success({
    text: message
  })
};
```
Before deploying test out the Action by click the Test icon. Once test is successful click deploy.

Then click **Add to flow** and drag the Action into the Post User Registration flow.

Add NPM Packages and Store Secrets with Auth0 Actions

After a user successfully logs in, Auth0 sends an ID token to your React application. You can use the data from the ID token to personalize the user interface of your React application. ID tokens issued by Auth0 are [JWTs](https://jwt.io) and you can add custom claims to the JWTs using Actions.

Create a Login Action to add the user metadata as a customer claim. 


```js
exports.onExecutePostLogin = async (event, api) => {
  const namespace = `https://myapp.example.com`
  const { favorite_ninja_turtle } = event.user.user_metadata

  if (event.authorization) {
    api.idToken.setCustomClaim(`${namespace}/favorite_ninja_turtle`, favorite_ninja_turtle)
  }
};
```
Auth0 allows namespaced and non-namespaced claims.To avoid name collisions, we recommend using namespaced claims. 

You can use any non-Auth0 HTTP or HTTPS URL as a namespace identifier.

Use a URL that you control as a namespace identifier; this allows you to avoid the risk that someone else is using the same namespace. The namespace URL does not have to point to an actual resource. It is only used as an identifier; it will not be called.

The JWT returned to the requesting application is built and signed at the end of the trigger running. The final, signed JWT is not accessible in an Action.

Check out the docs to learn more about [creating custom claims](https://auth0.com/docs/secure/tokens/json-web-tokens/create-custom-claims)

Add a Custom Claim To Auth0 JWT Id Token

Add a custom field to the users metadata with the [Pre User Registration trigger](https://auth0.com/docs/customize/actions/flows-and-triggers/pre-user-registration-flow).

In the Actions editor enter the following code
```js
exports.onExecutePreUserRegistration = async (event, api) => {
  api.user.setUserMetadata("favorite_ninja_turtle","raphael" )
};
```
This action uses the [API object](https://auth0.com/docs/customize/actions/flows-and-triggers/pre-user-registration-flow/api-object) to add the new metadata before the user is saved to the database

To learn more about Auth0 user metadata [read the docs here](https://auth0.com/docs/manage-users/user-accounts/metadata)



Write Action To Add Metadata To A New User Profile

With Actions you have the option to use pre-configured Actions from the [Auth0 Marketplace](https://marketplace.auth0.com/features/actions).

Add the [Country-based Access](https://marketplace.auth0.com/integrations/country-based-access) Action to your Action library to restrict users access based on their country. 

Once the Action is added to your library, choose the Login flow trigger. Use the drag and drop flow editor to add the Country-based Access Action to the Auth0 login flow.

Add Action from Auth0 Marketplace To Restrict Access By Country

Create a new application with the Auth0 CLI with the `auth0 apps create` command.

Name the application, create a description, and select the application type.

If you don't have an application set up with Auth0 you can run `auth0 quickstarts download` to download a sample application that's already configured with Auth0. 

Once the quickstart is downloaded open your code editor and open `src/auth_config.json` file and copy the domain and clientId from the settings inside the Auth0 dashboard, if they aren't population already.

Run `npm run start` to load the application on `localhost:3000` and test out the login flow.

Create New Auth0 Application and Download Quickstart

Download the Auth0 CLI on a Mac with homebrww with the command `brew tap auth0/auth0-cli && brew install auth0` 

For download instructions for Windows or Linux check out the [Auth0 CLI's README](https://github.com/auth0/auth0-cli)

When the CLI is installed use the command `auth0 login` to connect the Auth CLI to your Auth0 tenant. 

Install and Connect the Auth0 CLI to Auth0 account

Sign up for a free Auth0 account. A new Auth0 account creates a [new tenant](https://auth0.com/docs/get-started/auth0-overview/create-tenants) within the Auth0 Dashboard the tenant will house your applications connections and user profiles.

Sign up for a [free Auth0 account here](https://a0.to/egghead).

Create an Auth0 Account

Ethereum is a decentralized, open-source blockchain with smart contract functionality. 

ethereum

Welcome to Noah's course on Introduction to Smart Contracts with Ethereum and Solidity. 

Introduction to Introduction to Smart Contracts with Ethereum and Solidity

Web3 is a paradigm shift in how applications are interacted with, ran, and built. 

It’s not just a Pump-and-Dump scheme on cryptocurrencies or Bored Ape NFT profile pictures you can put on Twitter.

A fundamental tenet of Web3 is bringing ownership back to the user. You no longer have to trust that your data is being properly handled on someone else’s server (although, currently Web3 ecosystem mainly depends on centralized infrastructure such as GitHub).  

This ownership is achieved through blockchain, cryptocurrencies, NFTs, and smart contracts.

A great example of this type of ownership is through how you exchange money in Web3. There is no intermediary like Stripe, or PayPal to process your transactions. You can even build your own smart contracts that receive crypto (e.g. Ethereum or ‘eth’ for short) and then process that eth how you’d like.

Building this type of smart contract is exactly what Matías is going to show you how to do right now.

Matías builds out a Web3 application that allows you to receive tips in the form of eth in a tip jar on your website. This means your application will be backed by a smart contract that’s accepts eth, stores data, and emits Solidity events.

The frontend application uses SvelteKit which you’ll see how easy it is to get up and be productive with in minutes. A huge benefit here is that the JavaScript you write is just that, JavaScript. You’ll be able to take what you learn and implement it into any framework of your choosing.

While you build this application you will learn how to:

- Write a smart contract using Solidity language
- Test the smart contract using just JavaScript through the waffle framework
- Communicate and interact with the smart contract using ethers.js in a SvelteKit application
- Deploy your smart contract to make it public and accessible to anyone

Solidity is an object-oriented, high-level language for implementing smart contracts.

solidity

Full Stack Web3 and Blockchain Development on Ethereum with SvelteKit

There are several Ethereum test networks like Ropsten, Rinkeby and Kovan that you can use to deploy your contract to have it publicly available without having to use the mainnet and real ETH.
In this course you'll deploy to Rinkeby netwok (but, the process is the same for the other networks).

The first step will be update your Metamask Wallet to connect to the Rinkeby network.

Next, you'll need some test/fake Ethere to use for testing the Dapp in the network, for that you'll need to use a [faucet like this one](https://www.rinkebyfaucet.com/). Just visit that faucet and add your wallet address.

You will also deploy your web application to vercel to see your project live on the internet!

Deploy your Smart Contract to Goerli Test Network and App to Vercel

The magical disappearing UI framework

 - The web's JavaScript bloat crisis, solved. Svelte turns your templates into tiny, framework-less vanilla JavaScript.
 - Simple and familiar. Build apps out of composable, easy-to-write blocks using languages you already know.
 - Super fast, rock solid. Compile-time static analysis ensures the browser does no more work than it needs to.

svelte

Now that we have an application that is accepting tips to the smart contract that was defined, we need to be able to withdraw the funds that are sent to the contract. The smart contract function for this is already defined so we will just need to call the function from the front end.

To do this we will create a new route to display the contract information. We will then check if the current user is the contract owner and if so allow that user to withdraw the contract funds by clicking a button that we wire up to call the withdraw function from the smart contract.

## Important

SvelteKit is still in beta. Expect bugs! Read more here, and track progress towards 1.0 here. 

This lesson was recorded before the latest breaking changes, the content is still valid but it sometimes references a file that does not exists anymore.

Now: 
`src/routes/index.svelte` is called `src/routes/+page.svelte`

`src/routes/__layout.svelte` is called `src/routes/+layout.svelte`


Everything else is 100% valid. This particular content will be updated when Sveltekit reaches 1.0.0 stable.

Withdraw eth from a Smart Contract in a Svelte Application

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.

Use Gemini 2.0 to Create Agent Instructions to Refactor an Entire Codebase

Learn how to display custom components in a [Tanstack Table cell](https://tanstack.com/table/latest/docs/guide/cells), including how to render capitalized text, apply conditional styling with class helper functions, and format dates using the `Intl` API for readable display. 

`flexRender` allows you to utilize the `cell` callback method in your column definitions. Tanstack table will call this function to render the custom component you defined.

Render Custom JSX in a Tanstack Table cell

Use tanstack table flexRender method to render custom components in a table component. Capitalize letters, apply conditional styling, and render dates with Intl

I'm extremely excited for the potential of AI watching your screen while you work. I decided to take Google's AI Studio for a spin, which just introduced a feature called "Stream Realtime", which allows AI Studio to observe your screen and listen to your microphone while you work.

This video is my initial attempt to try and coach AI Studio through the process of building a site from a reference site, essentially trying to build egghead.io from a Next.js starter template. And we'll explore the various attempts we make and what works and what doesn't.

Let AI Watch Your Screen: Build Next.js Pages with AIStudio's Stream Realtime


[Shadcn](https://ui.shadcn.com/docs) is a popular component library that allows you to install components into your codebase.

Learn how to install the [Table component](https://ui.shadcn.com/docs/components/table) and use that presentational component with [Tanstack table](https://tanstack.com/table/latest).


Display Tabular Data in React with Tanstack Table

Build a dynamic table component in React using shadcn component library and tanstack react table.

TypeScript's satisfies operator finally clicked for me when I realized it's almost always used for specific implementations of configuration objects. So this lesson walks you through the naive approaches I've taken before and how to solve them using the satisfies operator. After this, satisfies will be another tool in your belt in TypeScript. To clean up all the TypeScript code you have around configuration.

TypeScript's "satisfies" for Configuration

Windsurf and Cursor are both able to take an image and then use an agent to build out what it sees in that image. This lesson is going to compare Windsurf and Cursor by uploading the same image to both and giving them the same prompt. Comparing not only the results, but also the steps that they take to get there. We'll also try uploading additional images throughout the process to see what they do as far as revising along the way and improving the site as they go along. 

Windsurf Cascade vs. Cursor Composer Agent: Build a Site from an Image

In this lesson, you'll discover how to style View Transitions using CSS pseudo-selectors to create custom animation effects. We'll transform the default cross-fade into a smooth slide transition by targeting the ::view-transition-old and ::view-transition-new pseudo-elements. You'll learn how these powerful selectors give you precise control over your transition animations, allowing you to create more engaging and personalized user experiences with just a few lines of CSS.

Customize View Transitions with CSS Using view-transition-old and view-transition-new

In this lesson, you'll learn how to implement smooth state transitions in your web applications using the browser's built-in View Transitions API. We'll create a simple example that demonstrates how to animate between different text states with just a few lines of code - no external libraries required. This powerful native API makes it easy to add professional-looking transitions to your user interface, enhancing the user experience with minimal effort.

Create Smooth UI Transitions with the Native View Transitions API

I've been using Cursor for a very long time and their "Agent" feature in Composer is fairly new, so I'm still getting used to it. But since Windsurf recently got onto the stage with their Cascade agent, they've slowly been gaining the mind share on the UX for coding agents. I decided to put them to the test by putting Windsurf and Cursor on the exact same screen side by side trying to accomplish the same task and to see which workflow I would prefer. I've been a diehard Cursor user for over a year now, so it's going to take a lot for me to switch to a different IDE. But I just have to say, even from this simple demo, Windsurf is looking pretty nice.

This lesson is just going to walk through creating a CLI using both tools to print out inspirational quotes and to explore how they approach the step-by-step of installing packages and running commands and setting up all the files we need to get this running.

Windsurf Cascade vs. Cursor Composer Agent Side-by-Side Comparison

I've been using Cursor as my primary editor for over a year now, but recently I've heard wonderful things about Windsurf AI Agent features. I decided to record myself building out something I've always wanted to make, but never made the time for.

In this lesson, I demonstrate how to leverage Windsurf's powerful agent process to create a fun word-guessing game inspired by Heads Up. Watch as I build an interactive application featuring category selection and word navigation, complete with data hosting on GitHub Gists and deployment to GitHub Pages - all in under 30 minutes (before editing the lesson down to 12 minutes)!

What makes this project particularly exciting is how Windsurf eliminates the typical friction points of development. While this game was always on my project wishlist, the overhead of setup, configuration, and deployment made it hard to justify the time investment. Windsurf's agent process handles all these pain points seamlessly, from managing URLs to orchestrating deployment.

This lesson perfectly showcases how AI agents can help developers bring their backlog of project ideas to life, transforming what would typically be time-consuming tasks into efficient, enjoyable development experiences.

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