Learn Jest, React-router and Svelte

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.

svelte

Up and running with Svelte 3

In this collection, we build a minimal flashcard application using React, primarily focusing on function components and the hooks API. To make sure we can understand and maintain existing code, there are also a few lessons toward the end that use class components so you can get familiar with the syntax. We cover important React concepts, and sprinkle in libraries that are pretty standard in the ecosystem like @reach/router, Jest, and React testing library. We start with create-react-app so we can get right into it without worrying about configuring tooling. There's [a separate course for that here](https://egghead.io/courses/modern-javascript-tooling-with-react?af=5mx0ie)

jest

Build a React App with the Hooks API

In this course we are going to work through properly setting up Enzyme with Jest to test rendered components. This includes the nitty gritty of making our testing environment work with various versions of React. After we get our environment setup ready, we’ll work through the different ways we can render a component within our test pages. With a rendered component we can now test component methods and properties to assert that they are what is intended. 

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

Test React Components with Enzyme and Jest

End-to-end testing assures you of a few things: that all the integrated pieces of an application properly function, all those pieces work together as expected, and your tests include and simulate real-user scenarios — something unit and integration tests just don't do.

This course introduces you to two great tools for E2E testing: 

* Puppeteer opens and runs applications in a Chromium browser and performs the actions it's given.
* Jest asserts that the integrated pieces work as expected and that add-on libraries like Faker and pixelmatch take our tests to the next level.

Over 9 lessons, we will create common application features and use Puppeteer and Jest to run different types of tests against them. You'll get practice using these tools to render content, mimic user activity, automate tests, and measure the overall performance of your application.

End to End Testing with Google's Puppeteer and Jest

React Router v4 takes an entirely new approach to routing and handling URLs in your React applications. It fully embraces the concept of declarative programming and a component based development process. In practice, this turns out to be very nice and gives you a routing solution that is less configuration heavy than many previous solutions.

In this course, you will learn about the basics of React Router v4 to help you get started. We will look at the core components that React Router supplies and how they interact together to create a robust routing solution for your React applications.

Add routing to React apps using React Router v4

React Router is the defacto router for any React application and it allows us to extract the state of our application from the browser's address bar.

In this course we'll explore the core features of React Router in common examples.  From routing with individual components to more complex routing consisting of multiple components, query-strings, route parameters,  and redirects.  

Getting Started with React Router v3

Best practices for building & testing redux applications have changed dramatically over time. This course aims to be a comprehensive and up-to-date resource for those seeking to confidently test their redux apps. Whether you're just getting started or want to improve on your existing testing strategy, there will be something in this course for you.

This first few lessons of this course look at how to add jest to an existing react/redux application that was built on top of [vite](https://vitejs.dev/). We cover basic functionality like using `npm test` vs `npx jest` and generating and using [code coverage](https://jestjs.io/docs/cli#--coverageboolean) to inform our testing strategy.

The next 10 or so lessons cover the specifics of unit testing the redux code in our application. We'll go over how to test reducers, selectors and thunks. As part of this we'll touch on mocking APIs and using [Redux Mock Store](https://github.com/reduxjs/redux-mock-store) as well as running actions through our applications' actual reducers to broaden our test coverage.

In the final part of this course we'll look at how we can test our redux connected react components using the various utilities that come with the [React Testing Library](https://testing-library.com/docs/react-testing-library/intro/). We'll cover simulating various kinds of user input with the [User Event Module](https://testing-library.com/docs/ecosystem-user-event), populating our redux store with test data, using [jest spies](https://jestjs.io/docs/jest-object#jestspyonobject-methodname), how to wait for asynchronous tasks to complete, and several approaches for finding & asserting that visual elements exist on the page.

This course is built on top of content that was created for the [Modern Redux with RTK and TypeScript](https://app.egghead.io/playlists/modern-redux-with-redux-toolkit-rtk-and-typescript-64f243c8) course and I highly recommend you start there if you haven't completed it already. It does expect a *basic* familiarity with react, redux and jest. TypeScript is used in these lessons, but is not a major focus and hopefully won't distract you too much if you prefer plain JavaScript.

No matter your experience level with redux and testing react applications, I'm confident your abilities will level up as you watch this course and follow along with the examples.

Thank you!

Confidently Testing Redux Applications with Jest & TypeScript

Here are all the Egghead.io lessons about testing with Jest! http://facebook.github.io/jest (https://kcd.im/egghead-jest)

Testing JavaScript with Jest

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

React Router v4 doesn’t require a lot of configuration to run. The core examples will run out of the box with Create React App. In this lesson, you will create an application and get React Router v4 up and running.

_**note**: in this video `react-router-dom` is installed with the `--save-dev` flag. This is **not required and may cause issues if used**. Simply install it with `npm install react-router-dom` and it will function as expected._

Run the React Router v4 Examples with Create React App

React Router 4 has several routers built in for different purposes. The primary one you will use for building web applications is the BrowserRouter. In this lesson you will import the BrowserRouter and create some basic Route components.

Create Basic Routes with the React Router v4 BrowserRouter

setRouteWillLeaveHook provides a method for us to intercept a route change before leaving the current route.

React Router: setRouteWillLeaveHook

React-router is the community favourite routing solution - it can handle all of your complex routing needs and in this lesson we’ll cover what’s needed to enable it’s use within Preact. https://github.com/ReactTraining/react-router

Integrate react-router with Preact

IndexRoute allows us to define a default child component to be rendered at a specific route when no other sub-route is available.

React Router: IndexRoute

We can use regular expressions to more precisely define the paths to our routes in React Router v4.

Use Regular Expressions with Routes with React Router v4

In this lesson we'll look at hashHistory which uses a hash hack to track our route changes vs browserHistory which delivers clean urls, but requires server work to implement

React Router: hashHistory vs browserHistory

Since react-router routes are components, creating nested routes is as simple as making one route a child of another in JSX.  In this lesson we'll explore nesting routes and accessing the children of parent routes.

React Router: Nested Routes

A router library is no good if we have to hardcode every single route in our application.  In this lesson we look at how to access variables in our routes and pass them into our components.

React Router: Route Parameters

In this lesson we'll learn how to render multiple component children from a single route.

React Router: Named Components

The Redirect component in react-router does exactly what it sounds like.  It allows us to redirect from from one route to another.

React Router: Redirect

If you’ve created several Routes within your application, you will also want to be able to navigate between them. React Router supplies a Link component that you will use to make this happen.