Learn Recoil, Recompose and Svelte

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.

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Getting Started with Recoil in React

[Recoil](https://recoiljs.org/) is a brand new state management library for React, developed by Facebook.

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

This quick collection will get you up and running with Recoil, you're going to learn how to:

* add Recoil to your React project
* create a Recoil atom and use it to store a piece of state
* use `useRecoilState` hook to update an atom
* use `useRecoilValue` to access value stored in an atom in a read-only fashion
* use 🔥`selectors`🔥 in order to calculate derived data based on state stored within atoms (this is *really* powerful!) 

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

Sync State Across Components with Recoil in React

JavaScript community has been shaken recently by a release of Svelte 3 and for a good reason - it's a completely different approach than React or Vue. To quote the docs:

"[Svelte](https://svelte.dev/) is a radical new approach to building user interfaces. Whereas traditional frameworks like React and Vue do the bulk of their work in the browser, Svelte shifts that work into a compile step that happens when you build your app."

**The best part?** If you have 26 spare minutes you can learn the basics of Svelte 3 and start building your own apps with it!

Enjoy!



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.

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Up and running with Svelte 3

***Note: Active maintenance for Recompose has been discontinued since the announcement for React hooks. Your existing code using Recompose will still work. Recompose is not compatible with RxJS version 6 and beyond. You can read more about the decision [here.](https://github.com/acdlite/recompose/issues/756#issuecomment-438674573)*** 


Loading data and handling events almost always introduces layers of complexity into React apps. Recompose and RxJS solve your async problems by using Streams to output components. This course walks you through combining the powers of React and RxJS to stream data into JSX with streaming patterns and pure React components.

Build React Components from Streams with RxJS and Recompose

In this course, you will learn to use many of the most powerful and convenient higher-order components within Recompose by coding several real-world examples. Using recompose looks very different from “vanilla” React; so you will also get comfortable with the look and feel of a “recomposed” component. The best part is no more need for class components! You’ll learn how to use Recompose to both modify components and also create your own higher-order components.

Higher Order Components with Functional Patterns Using Recompose

In this free collection on Facebook's new state management library, we'll get started using Recoil in our React applications and then delve into various common use cases that we may encounter in the field.

We'll start with the basics of state management in Recoil: the Atoms and Selectors. Then we'll dive further into the Selector API, an important part of the library. Along the way we'll learn different strategies for handling synchronous and asynchronous Selectors.

Manage React State with Recoil

Creating forms is one of the simplest and most complicated things at the same time. A basic form consists of many different things happening, we have to retain the value, we have to keep watch of validation and we have to show error messages when something is invalid, this is on both the fields and on the entire form itself if we send a request off to the backend service.

So we're going to create a form using just the normal svelte features. Then we'll look into creating a form using the svelte forms lib. 

Create forms in Svelte with Svelte Forms Lib

When you declare your Component and Props in JSX, you can pass those props along to your [RxJS](/q/rxjs) stream. This is typically done using `switchMap` or `combineLatest` where you can grab from the props from your `props$` stream and push them into another stream.

Pass a React Prop to a Stream in RxJS

Svelte is a new approach to building user interfaces. 

Instead of doing the vast majority of work at the runtime as other frameworks do, Svelte shifts that work into the _compile_ step which happens when you build your app. As such, you're shipping heavily optimized code to your users.

In this quick lesson we are going to learn how to create a brand new project with Svelte 3 from scratch.

Create a new project with Svelte 3

In most Web applications we want to be able to render different HTML markup depending on values passed in from JavaScript code.

In this lesson we are going to learn how to render JavaScript variable in HTML markup when using Svelte 3.

Add data to HTML markup using Svelte 3

In Svelte 3, the same as in regular HTML we can add CSS styles to a component and this is what we're going to learn in this lesson.

Important note - styles are _scoped to the component_ which means that if we style a `h1` tag in component A, it won't automatically affect `h1` tags in component B.

Add styles to Svelte 3 component

It's highly unlikely that we'd like to have an entire app in a single file. Instead, what we'd like to do is to spread our code across multiple components and render them in one another.

In this lesson we are going to learn how to create a `<Surname />` Svelte 3 component which we're going to use in our main `App.svelte` file to display a user's surname.

Create a new Svelte 3 component to render it inside of another component

One of the key advantages of having a component system is the ability to render the component differently based on what kind of properties (shortened to 'props' in Svelte) were passed in to the component.

In this lesson we are going to learn how to declare properties inside of a Svelte component and how to pass in data to be rendered inside of a `<UserInfo />` component. We're also going to learn how to use default props which are used if a value for a property was not passed in.

Declare and pass in properties to a Svelte 3 component

Svelte automatically updates the DOM when your component's state changes. Often, some parts of a component's state need to be computed from other parts. This is where _reactive declarations_ come in.

In this lesson we are going to learn how to use reactive declarations to re-compute (and render) square of a counter value in a simple counter example whenever user clicks on a button.

Use reactive declarations to compute component state in Svelte 3

Quite often we need to be able to loop over and render a list of data that (for example) is returned from the backend. 

In this lesson we are going to learn how to use `each` block from Svelte to iterate over a list of data and render a list of European cities. We're also going to learn how to get the current `index` while iterating over a list, as well as how to destructure a currently iterated over element of the array.

Loop over and render a list of data using an `each` block in Svelte 3

The whole magic of webapps is that users can interact with our code via various DOM events and Svelte is no exception in that regard.

In this quick lesson we're going to learn how to use DOM events in Svelte 3 as well as how to use event _modifiers_ to alter DOM event behaviour (such as `once` and `preventDefault`)

Use DOM events and event modifiers in Svelte 3

Every Svelte component has a lifecycle that starts when it is created, and ends when it is destroyed. There are a handful of functions that allow you to run code at key moments during that lifecycle.

The one you'll use most frequently is `onMount`, which runs after the component is first rendered to the DOM. 

In this lesson we're going to learn how to use `onMount` to fetch and render data from Star Wars API.

Use an onMount lifecycle method to fetch and render data in Svelte 3

Not all application state belongs inside your application's component hierarchy. Sometimes, you'll have values that need to be accessed by multiple unrelated components, or by a regular JavaScript module.

In Svelte, we do this with _stores_. In this lesson we're going to learn how to create a `writable` store and how to use it to allow `Incrementer` and `Decrementer` components modify the value of the store

Use Svelte 3 stores to share data between multiple unrelated components

Sometimes we don't want to have a complicated `update` function to change a value of our store. We know exactly what we want to change the value to - we can just use the `store.set` function to do that.

In this lesson we're going to learn how to set a value to a Svelte 3 store by using the `store.set` function to set the value of a counter without having to increment/decrement it one by one.

Set a value to a Svelte 3 store

It's important to avoid memory leaks, and Svelte 3 is no exception. When we're using the `subscribe` method from Svelte store in a component, it's important to clean ofter ourselves (especially if we're going to instantiate and destroy this component many times over).

In this lesson we're going to learn how to use `unsubscribe` to stop subscribing to the store change in a component's `onDestroy` call, as well how to use auto-subscriptions to refer to the store value and let Svelte take care of cleaning after us to avoid memory leaks.

Use auto-subscriptions in Svelte 3 to avoid memory leaks when using Stores

If our app needs to display values that are dynamically changing, it's better to animate that to deliver a more engaging user experience.

In this lesson we're going to learn how to use a `tweened` value to dynamically update the value of a progress bar in Svelte 3.

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