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

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 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

Mock Service Worker is an API mocking library that allows you to write client-agnostic mocks and reuse them across any frameworks, tools, and environments.



Mocking WebSocket APIs with Mock Service Worker


When attempting to load the same module twice in JavaScript you'll hit a cache and code won't re-run. In scenarios where you actually do want to have state in your modules, you'll have to use a cache-busting technique by passing a query parameter to a dynamic import. This lesson walks through how to add a query parameter, how to add the appropriate types for loading dynamic modules in TypeScript, and when these techniques are valuable.

Import the Same JavaScript Module Multiple Times with Cache Busting



The include keyword in GitHub Actions empowers you to add custom variables to your matrix strategy, providing flexibility beyond standard configurations. In this video, we'll explore how include allows you to define specific combinations of variables, enhancing control over your workflow runs. You'll see how this feature enables you to tailor jobs for unique environments or scenarios not covered by the default matrix options. By leveraging include, you can efficiently manage complex build processes with greater precision. This technique helps you streamline your CI/CD pipeline, making it more adaptable to your project's evolving needs.

Use GitHub Actions Matrix Include for Complex Job Configurations

While running `zod` schema validation agains domain-rich objects, the error message saying that _a string is not a number_ might not be really useful.

Especially, when you need to provide a meaningful feeback to the user, e.g. after they have submitted a form with lots of data.

`zod` allows to customize messages on a very granular level. We can also extract repeatable customization to `zod` error maps.

Finally, in order to process an error message further (e.g. display it to the user), we need to handle the `zod` validation errors effectively. Especially, when a big object validation has failed and we could receive a handful of errors.

That's what we learn in this lesson. 🔥

Customize zod Error Messages and Handle zod Errors Effectively

customize zod validation messages, customize zod schema property messages, reuse error maps across different schemas, navigate through zod error objects

You might want to run `zod` schema checks in different styles.

Sometimes you prefer to conditionally throw the error - that's what `parse` does. But another time you'd prefer to receive a `boolean` property that determines whether the validation was successful or not - and perform further actions accordingly.

Additionally, the error-throwing API of `parse` works extremely well with [TypeScript assertion functions](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-7.html#assertion-functions). Their combination is just... perfect! 👌

That's what we learn in this lesson.

Use parse and safeParse Runtime Type-checks with zod

use zod parse function to conditionally throw ZodError, use zod safeParse to get a boolean value and run typescript type guard over success property

In this lesson we learn that TypeScript cannot guarantee correct shapes of responses. That's due to TS performing checks in compile-time, while the response will be availbale in runtime - when TS doesn't exist anymore.

In some situations, such as HTTP requests, runtime type checks such as `zod` are essential for providing quick feedback around data-related errors.

Understand where are the possible mistakes to make while using TypeScript with HTTP calls. Use `fetch` and `axios` along with `zod` schema checks.

Also, note that similar mistakes or mistakes could happen while using web storage (e.g. `localStorage`)

Validate HTTP API Response with zod, fetch and axios

use zod as an HTTP response validation tool along with fetch and axios in order to make sure that the response has expected data structure

In this lesson we learn that the `zod` schemas become the single source of truth.

We shall not update TypeScript types manually, since they are generated automatically from the schema.

Same with validation functions.

Whenever the schema changes, all the rest will update accordingly. It's an important mind shift.

Treat zod Schemas as Single Source of Truth

Zod Schemas are the single source of truth for both typescript types, and interfaces - and runtime validation functions. Schemas should be updated first.

`zod` is powerful, but writing the schemas manually for existing JSON objects, especially big ones, can be time-consuming.

But that's what `quicktype` is for! You can get 80% work done instantly! 🥳

Depending on your need - whether you want to automate the process, or do it just one time, you can:
- use an online app
- use an IDE extension
- run a CLI script
- generate a script to be executed within CI/CD environment/tooling

And this is what we learn in this lesson! 🔥🔥🔥

Get started with zod quickly!

Generate zod Schemas Automatically using Quicktype App, Extensions and Scripts

Use quicktype app, extension or scripts to automatically generate zod schemas from existing json files. Save time and get started with zod quickly!

`zod` is a powerful library allowing to run runtime type-checks.

It's complementary to TypeScript, which does type checks in compile time.

In this lesson we create few schemas that represent primitive type values, along with `zod` utilities which make these more precise. We also create object schemas and nest one inside another.

All schemas are being validated against example values. We analyze how to interpret error messages in case of failures.

Perform Runtime Type-checks on Primitives and Objects with zod

Create zod schemas to validate primitive type and object type values in runtime. Analyze the errors to see how a value doesn't correspond to schema expectations


Using Cursor Chat, you can easily reference an entire directory of files and ask it to generate anything based on those files. This opens up the possibility of using your current code as a reference guide to create new code that follows existing patterns. With this approach, the result can be a polished prompt you can use with any AI to generate consistent and reliable output.

Focus less on crafting the perfect prompt upfront - what matters most is testing and iterating based on the AI's responses. The more results you see from the prompt, the more you can reinforce the good results and prune out the bad results until your prompt is polished enough that you can rely on the prompt to give you consistent quality results.


Chris Achard

React Crash Course with Hooks

Featured Courses

Search Results

Append two strings together in javascript (with edge cases)

Use Async Functions in a Recoil Selector

Getting Started with Recoil in React

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

Compute a Value in Recoil Using a Selector

Read a Value from Recoil with useRecoilValue

Create Shared State with Recoil in a React App

Set Up Recoil in a new React App

React Crash Course with Hooks

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

Adding Styles to React Components with CSS or Inline Styles

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

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

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

Reusing Custom React Components by Passing Data Down as Props

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

Write a Custom Function Component in React with JSX

Think in React by Breaking Your UI into Components

How React Works

Write Your First React Component with CodeSandbox.io

Copy a Commit from One Branch to Another