Learn Chrome-devtools, React-native and Solidity

React Native lets you build mobile apps using only JavaScript. It uses the same design as React, letting you compose a rich mobile UI from declarative components.

react-native

Use Expo Orbit to install past builds from EAS as well as from your local machine.

You can also use Orbit to easily view and launch all your connected simulators, emulators and physical devices.

🔗 [Expo Orbit](https://docs.expo.dev/build/orbit/)

Use Expo Orbit to Install Past Builds

Reconfigure your eas.json and app.json so you can install the development, preview and production builds all on the same device.

An app on your phone is uniquely identified by the bundle identifier on iOS and the package on Android, so to make the builds unique we have to make these IDs different based on the build profile.

📖 [Docs](https://docs.expo.dev/build-reference/variants/)

Install Multiple Variants of Your iOS and Android Apps on the Same Device

Set up credentials to upload your Android build to Google Play automatically.

For automatic uploads, you'll need to set up all the app metadata on your Google Play account, including setting up app assets. You'll also need to configure and set up a Google Service Account.

📝 [Create a Google Service Account](https://github.com/expo/fyi/blob/main/creating-google-service-account.md) 
📝 [Store Assets](https://docs.expo.dev/guides/store-assets/)
📝 [EAS Submit Docs](https://docs.expo.dev/submit/introduction/)

Upload an Android App to the Google Play Store Automatically using Expo Publish

Set the build number to increment automatically and learn when to increment version numbers.

While you’re developing your app, when you submit an app with a specific version + version code to the App or Play Store, you cannot submit another app with the same values.

The best practice is to set the build number to increment automatically.

The version number can be incremented manually after each store release.

📖 [Docs](https://docs.expo.dev/build-reference/app-versions/)

Increment Version and Build Numbers for iOS and Android apps using EAS

Create the app on the Google Play Store, create the first production build on EAS, upload it to Google Play, and publish it to an internal testing group.

For sharing apps via Google Play, you will need a paid Google Play developer account. It is preferable to have an organisation account if you're looking to monetise your app (you'll need to verify your organisation before you can create apps). But if you you are building apps as an individual developer, you can use the individual developer account. 

When creating an individual developer account, you have some additional restrictions:
1. You must submit proof of ID and home address to create the account
2. If you want to monetise your apps, your home address will be shown on the Google Play developer page
3. You will need 20 testers to test your app for 14 days before you can apply for production access

🎮 [Google Play Console](https://play.google.com/console)

🔗  [Register for a Google Play Developer account](https://support.google.com/googleplay/android-developer/answer/6112435)

🔗 [Required information to create a Play Console developer account](https://support.google.com/googleplay/android-developer/answer/13628312?hl=en-GB)

🔗 [QR Code Generator](https://www.qr-code-generator.com/)


Create an Android Release Build with EAS and Upload to Google Play Store

Create an Internal Distribution (Preview) build for sharing your app in internally in production mode.

This can be used to share your build with your team or testers without submitting it to Google Play.

📝 [Docs](https://docs.expo.dev/build/internal-distribution/)

Create an Internal Distribution Build for Android with EAS

Create a Development Build that runs on Android Emulator or Device.

This build can be used for local development on Android. You can use the same apk (the build artifact) on both an Emulator (that you can install via Android Studio) or on a real android device.

🔗 [Expo Website](https://expo.dev/)

📝 [Docs](https://docs.expo.dev/build/introduction/)

🔗 [Android Studio](https://developer.android.com/studio)

Create a Development Build for Android with EAS

Submit your Production Build to the Apple App Store and install it via TestFlight.

When submitting a build to Apple with EAS Submit (or otherwise), it will first get added to TestFlight which is essentially a pre-prod environment for Apple. This will allow you to install and share the actual production build to testers before releasing it to users.

App names on the Apple App Store must be globally unique. So if you've chosen a name for your app that is already taken - like Plants - you will have to choose a different name for the App Store Listing page. Note that this is only the case for the app name on the App Store listing page, and you can still use your preferred name elsewhere.

**TestFlight Internal Testing** - as soon as you upload your build to App Store Connect and it finished processing, it is available for internal testing. You can add users to the internal testing group by email, and the users must be registered on your Apple Developer account.

**TestFlight External Testing** - this is a separate testing group that allows you to share the build with anyone either by sending them an email invite or using an invite URL. Before you can share the build, you must first submit a build for external testing and wait for it to be approved by Apple, which usually takes a couple of hours.

**Release** - in order for the build to actually show up on the Apple App Store, you will need to create a Release on App Store connect and submit it for review. This review usually takes about a day.

🔗 [TestFlight](https://developer.apple.com/testflight/)

📝 [EAS Submit Docs](https://docs.expo.dev/submit/introduction/)

📝 [App Store Assets Docs](https://docs.expo.dev/guides/store-assets/)

Submit an iOS App to the Apple App Store and TestFlight using EAS

Create an iOS Release build for distribution.

This build gets submitted to the Apple and can only be installed via TestFlight or the App Store.

Create an iOS Release Build for the Apple App Store with EAS

Create an Internal Distribution (Preview) build for sharing your app in internally in production mode.

This is the only way to share your iPhone app without submitting it to TestFlight and is often used for QA testing or internal demos.

📝 [Docs](https://docs.expo.dev/build/internal-distribution/)

Create an Internal Distribution Build for iPhone with EAS

Create a build to run on your physical iPhone device that can also be used for local development.

📝 [Enabling Developer Mode](https://docs.expo.dev/guides/ios-developer-mode/)

📖 Further reading: [Push Notifications Docs](https://docs.expo.dev/push-notifications/overview/)

Create a Development Build for iPhone With EAS

Set up a Distribution certificate and an Ad Hoc provisioning profile for iOS internal distribution builds.

Here we learn how to sign Apple app builds to make them installable on Apple devices.

In order to install your own app on any Apple device, you need an Apple Developer account and a subscription to the Apple Developer Program.

🔗 [Apple Developer Program](https://developer.apple.com/programs/)

⚙️ [Code Signing Illustration](https://www.linkedin.com/posts/kadi-kraman_an-illustration-of-what-code-signing-with-activity-7132420058076581888-s6TM)

Use the EAS CLI to Configure App Store Credentials for Internal Distribution Builds

Create an iOS build for developing locally on a Simulator.

This is the only native iOS build you can do on EAS without having an Apple Developer account and being enrolled in the Apple Developer Program.

It can be used for local development on an iOS simulator, so you can only do this on a Mac, because you must be able to install Xcode to get access to the iOS simulators.

⚙️ [Xcode](https://apps.apple.com/us/app/xcode/id497799835)

🔗 [Expo Website](https://expo.dev/)

📝 [Docs](https://docs.expo.dev/build/introduction/)

Create a Development Build for iOS Simulator with EAS

Set up an existing Expo Go project to use Development Builds.

Expo Go is a Sandbox Environment designed for learning prototyping and getting started with mobile development quickly. The major limitation of Expo Go is that you are completely unable to add or edit any native code in your app. This might be a trivial limitation at the start of your project when you're prototyping and experimenting, but most production quality apps will eventually need to have more control over their native app bundles.

This is where development builds come in. A development build is basically your own customised version of Expo Go: you build the native side of your app yourself and get to have all the control over what libraries and configurations are included.

Thanks to CNG (with prebuild) the native projects are generated automatically based off of your app config and package.json.

📝 [Expo Go](https://docs.expo.dev/get-started/expo-go/)

📝 [Development Builds](https://docs.expo.dev/develop/development-builds/introduction/)

📝 [Continuous Native Generation (CNG)](https://docs.expo.dev/workflow/continuous-native-generation/)

Set Up Your Expo Go Project to Use Development Builds

Create a new React Native project using the Expo CLI.

You can use any of the supported package managers: **npm**, **yarn**, **pnpm** or **bun**. In the video (and throughout the course) we use **yarn**.

You can also choose a template to use for your project. In this video we choose the blank TypeScript template, but you can choose a different template if you prefer.

📝 [Docs](https://docs.expo.dev/get-started/installation/)

Create a React Native App With Expo CLI

Expo Application Services ([EAS](https://expo.dev/eas)) is a cloud build service used to build and publish React Native apps.

This course will show you how to create the common types of builds for iOS and Android on EAS. We'll cover Development builds for local development, Preview builds for internal testing, and Production builds for release.

Additionally, you'll learn about:
- app versioning
- automatic store uploads
- setting up store listing pages
- installing multiple app variants on the same device
- installing past builds with [Expo Orbit](https://docs.expo.dev/build/orbit/)

## iOS

An overview of build signing, and why an Apple Developer account needed in order to install builds on a real device.

How to create:
- an iOS simulator build
- a build to use on your device for local development
- a build to share with your team without uploading it to App Store Connect
- a release build to use on the App Store

You will also learn how to upload your build to App Store Connect, share it on TestFlight and create a Release.

## Android

How to create:
- a build to use for development on an emulator or a device
- a build to share with your team without uploading it to Google Play
- a release build to use ob Google Play

We'll cover what is needed to create a new Google Play account, and the current restrictions for individual accounts.

You will also learn how to set up auto-submit on Google Play.

Build and Deploy React Native Apps with Expo EAS

WAI-ARIA, the Accessible Rich Internet Applications Suite, defines a way to make Web content and Web applications more accessible to people with disabilities. It especially helps with dynamic content and advanced user interface controls developed with Ajax, HTML, JavaScript, and related technologies. 

aria

Debug Computed Accessibility Properties with Chrome Dev Tools

In this lesson, we use the element inspector in Chrome to test and improve our contrast to meet WCAG AA Contrast Ratio Standards.

Resources:
- [WebAIM - Contrast and Color Accessibility](https://webaim.org/articles/contrast/)

Debugging Accessible Contrast with Chrome Dev Tools

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

Learn how to test custom ESLint rules with Vitest and RuleTester.

In the [previous video](https://egghead.io/set-up-a-custom-es-lint-rule~kq49h), we created a custom eslint rule that gives us a warning when some of the class names don’t start with a lowercase letter.

Here, I'll show you how to test this or any other custom ESLint rule using unit tests without manually restarting the ESLint server or modifying production code to check if the rules work correctly. We'll look at the structure in which correct and incorrect code samples should be specific to RuleTester.

We'll also learn how to make our rule fixable and verify that the applied fix works as expected.

Ákos Kőműves

Test Custom ESLint Rules with Vitest and RuleTester

Learn to test a Custom ESLint Rule using Vitest and RuleTester.

This course is designed to make you proficient in building dynamic data tables in React using TanStack Table. 

You'll learn to fetch and display remote data, handle pagination, and implement row virtualization for better performance. 

The lessons guide you through customizing table cells with your own JSX components, adding features like toggling column visibility to enhance user interaction, and create mobile-friendly tables with CSS pseudo-elements. 

By the end, you'll have the skills to create efficient, user-friendly tables that elevate your React applications.

Ian Jones

Headless, Mobile-friendly Data Tables with Tanstack Table and React

Learn to display, paginate, and virtualize data effectively in a table with Tanstack table and React 19.

Install `ghx` with `npm i -g @johnlindquist/ghx`

https://github.com/johnlindquist/ghx

You've copied and pasted code, set up your project, and... *error*.  "Stream is not readable."  Sound familiar?  Generic Google searches and outdated Stack Overflow answers often leave you more confused than when you started.  You need more than just documentation; you need *context*.  You need to see how real developers solve this *exact* problem.

This lesson shows you a better way to debug, using real-world GitHub examples and the power of Cursor's Composer.

Here's the workflow we'll cover:

1.  **Identify the Error:** You've already done this!  You have a specific error message ("Stream is not readable") and the code that's causing it.
2.  **Find Real-World Solutions with `ghx`:** We'll use `ghx`, a tool for searching GitHub, to find *actual projects* that have encountered (and solved!) this same issue.  No more generic advice – you'll see working code.
3.  **Consolidate and Analyze:**  `ghx` brings those relevant code snippets into a single, easy-to-read file.
4.  **Leverage Cursor's Composer:** We'll use Cursor's Composer to directly interact with the examples and your problematic code.  Paste in your error, reference the `ghx`-generated file, and ask targeted questions like:
    *   "Based on these examples, how should I modify my code to fix the 'stream is not readable' error?"
    *   "What's the common cause of this error in the context of an MCP server?"
    *   "Show me the specific lines in the examples that handle stream readability correctly."
5. **Fix the Error:** Implement the solution using this workflow.

Instead of guessing, you'll learn directly from proven solutions.  You'll gain a deeper understanding of your issue and how to troubleshoot it effectively.  This approach transforms debugging from a frustrating hunt into a targeted learning experience.

John Lindquist

Fix Real-World Coding Errors with GitHub Context through ghx and Cursor Composer

AI is amazing for generating code, but often leaves us staring at functions and libraries we've never seen before. This creates a huge problem: When things break (and they will break), we're lost. We don't understand the individual pieces, let alone how they interact. Knowing one part isn't enough; we need to see how unfamiliar components work together.

The solution? Real-world examples.

This lesson introduces ghx, a tool I built to do exactly that. ghx searches GitHub, finding actual code examples that use the specific combinations of functions and libraries that are tripping you up. Instead of generic documentation, you get concrete implementations. You can find the ghx repository at https://github.com/johnlindquist/ghx.

Here's the workflow we cover:

Identify the Unknown: Pinpoint the AI-generated code you don't understand – specific functions, libraries, or their interactions.

Search with ghx: Use ghx to search GitHub for examples using those terms together. ghx finds repos where those elements co-exist.

Consolidate Examples: ghx combines the relevant code snippets from those examples into a single, digestible file.

Ask the AI (Again, but Better!): Feed this consolidated code to an AI (like a coding-focused model in an AI studio). Now, instead of asking general questions, you can ask targeted questions based on real-world usage:

"Explain how these functions are used together in these examples."

"What are some common use cases for this combination of libraries?"

"Show me alternative code snippets that achieve the same result."

"Can you identify potential problems or areas for improvement, based on these examples?"

Iterate. Use your improved understanding to make changes, and then repeat the process to debug.

By leveraging ghx and targeted AI prompting, we transform from being lost in a sea of unfamiliar code to actively learning from how others have solved similar problems. We gain a deeper understanding of our AI-generated codebase, making debugging, modification, and future development far more manageable. This gives you the tools to understand, debug and improve your own code.

How to Work with AI-Generated Code You Don't Understand with ghx and Gemini

In this less we create a custom Zod schema using `z.custom`.

The example case covers room numbers validation: it must start with an uppercase letter followed by three digits. `z.custom` allows the creation of a brand new custom schema with a callback function that returns a boolean indicating validity.

We highlight a challenge with type inference in Zod's custom schemas: callback parameter types don't get aligned automatically - type-safety must be explicitly defined using type parameters.

We run tests against various room numbers and demonstrate how to effectively validate inputs and manage error messages.


Tomasz Ducin

Create Custom Zod Schemas and Validate project-specific data

Create custom validation logic in Zod using z.custom, for primitive values, ensuring type safety and proper error messages for room numbers.


Excessive properties refer to any additional attributes that are not explicitly listed in an object schema. When creating an object based on a schema, it is important to ensure that only the defined properties are included.

In TypeScript, if an object is created with an extra property that isn't defined in the schema, TypeScript will not raise an error unless the type is explicitly annotated. When the type is annotated, TypeScript will issue an error indicating that the extra property is not allowed.

Zod provides a strict utility to enforce similar checks. This feature ensures that only specified properties are allowed in an object schema. When unnecessary properties are added at both the top level and within nested schemas, Zod will throw errors indicating unrecognized keys.

Adding an unrecognized property to a Zod schema results in an error message that specifies which keys are not recognized. Applying strict checks on nested schemas ensures that all levels of the data structure are validated correctly.


Make Excessive Object Properties Fail on Zod Validation

Prevent excessive properties in TypeScript and Zod schemas using strict checks for better data validation

In this lesson we discuss how Zod works with TypeScript to handle special types like `undefined`, `null`, `any`, `unknown`, `never` and `void`.

We modify our room booking schema to demonstrate the use of `optional` and `nullable` Zod utilities.

By using `.optional`, we allow a property to be either its _original type_ or `undefined`. With `.nullable`, we allow it to be either its _original type_ or `null`. Finally, `.nullish` allows a value to be either its _original type_, `null`, or `undefined`.

For all cases, we run tests to show how these schemas work in practice, as well as how TypeScript infers types.


Declare Lack of Value in zod (optional, nullable and nullish)

use Zod for TypeScript schemas, including handling undefined, null, and special types like optional and nullable values, as well as any, unknown never and void

In this lesson we make use of partial validation of large and nested schemas in Zod.

Instead of creating many small schemas, which can complicate maintenance, Zod allows for the extraction of specific parts of a schema using the concept of ".shape". It "unwraps" the object schema, enabling access to sub-schemas within specific properties.

Additionally, we can use the `.unwrap` to get into element schemas of altered schemas such as `.optional` or `.array`.

Simplify working with complex schemas without the need to break them into hundreds of small schemas.

Use Zod Schemas partially using shape and unwrap

Manage large and nested Zod Schemas by extracting partial validations using shape and unwrap utilities

In this lesson we cover implementing sets and maps in Zod.

Using `z.set`, a schema for string-based amenities is created. We demonstrate how validation works by intentionally introducing errors and customizing error messages for better clarity.

Next, a map is created for existing guestDetails schema using `z.map`, with string keys and an existing `z.object`-based schema. The validation process is shown again by deliberately breaking the schema, such as omitting the age property, which triggers appropriate error messages.


Validate maps and sets using Zod schemas

Use sets and maps in Zod for schema validation, ensuring type safety for both keys and values.

In this lesson we'll use a few predefined schemas which will serve as constituents to create union and intersection schemas.

Three room booking schemas are defined: _single_, _double_, and _suite_. Each schema has slight differences in the structure.

The `z.union` utility is used to create a union of these schemas, allowing for validation against any of them. Type inference (using `z.infer`) for the room booking schema produces a union of object literals, exactly like in TypeScript.

We also create an intersection using `z.intersection`, combining room booking details with discount information.

These techniques enhance data validation and allow to make `zod` aligned even more with `TypeScript`.


Define Unions and Intersections with Zod

implement unions and intersections in Zod schemas for example domain related objects, enhancing TypeScript validation with clear examples

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