Learn Immutable, 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

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

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

Immutable.js provides many Persistent Immutable data structures including: List, Stack, Map, OrderedMap, Set, OrderedSet and Record.

immutable

There are lots of techniques for accessing data kept in your Lists. In this lesson, we will compare how data stored in collections can be accessed directly in both standard Arrays and ImmutableJS Lists. We will also look at how to find data inside an Immutable List using the `findEntry` and `findIndex` methods.

Get items in an ImmutableJS List

The reduce function in ImmutableJS allows you to transform and create new data from an existing data structure. In this example, we will do some math and calculate a sum based on data in an ImmutableJS Map.

Calculate a sum using reduce in ImmutableJS

The key to being productive with Immutable JS is understanding how to update values that are nested. Using `setIn` you can place a new value directly into an existing or new path. If you need access to the previous value before setting the new one, you can use `updateIn` instead. `updateIn`  accepts the same path lookups as `setIn`, but gives you a callback function instead so that you can use the previous value however you wish and return an updated version.

Updating nested values with ImmutableJS

ImmutableJS reduce functions can be nested to get data out of complex data structures. In this example, we will create an Immutable List from an Immutable Map that is nested inside of an Immutable List that is itself nested inside of an Immutable Map.

Create a list with nested reduce functions in ImmutableJS

By utilizing immutable data structures, we can write code that is easier to reason about, avoid mutation-related bugs, reduce complexity, and even gain some performance benefits along the way.

Before diving too far into Facebook's [Immutable.js](https://facebook.github.io/immutable-js/) library, let's take a moment to examine some of the pains and obstacles that mutable data structures present. 

We'll take a brief glimpse at putting the Immutable "List" data structure to work by example. We will convert our usage of Javascript's native `Array` to use [Immutable.List](https://facebook.github.io/immutable-js/docs/#/List) in order to address a mutation-related "bug" caused by multiple objects "sharing" a mutable structure (array) by reference.

Immutable.js: Introduction - Easing the Pains of Mutability

In this lesson we'll look at some of the differences between standard JavaScript Arrays and Immutable Lists. We'll create Immutable.JS Lists from scratch, as well as by converting regular Arrays. We will also compare and contrast the `push` and `concat` methods between both types of collection.

Create an immutable List using Immutable.js

React Router is a complete routing library for React.

react-router

In this lesson, we’ll install React Router as a project dependency and add links that will update the url via pushState to avoid reloading our page on changes.

Add React Router to a Redux Application

In this lesson, we’ll wire up React Router to pass a url based filter parameter into our component and create a selector function to filter our state data between the store and our components by hooking into the `ownProps` parameter of `mapStateToProps`.

Filter State Data in Redux with a Selector Function and React Router

In this lesson we'll use the `match.path` value passed in by React Router to setup dynamic routes for Tabs. This will allow us to setup dynamic tabs which can be navigated to based upon the URL. With this pattern we can change the base path and our tab routes will automatically match and render correctly.

Create Nested Tab Routes with Dynamic Paths with React-Router

In this lesson we'll show how to setup the Prompt component from React Router. We'll prompt with a static message, as well as a dynamic method with the message as a function. Finally we'll show that you can return `true` from the message as a function to dynamically allow navigation.

Prevent Navigation with the React Router Prompt Component

In this lesson we'll show how the Link component `to` prop can receive an object. This allows  us to pass `state` to the route. With the nav state we destructure off of location we can determine if a user wants to open a modal or on a cold visit show an image embedded in the page.

Create a Modal Route with Link and Nav State in React Router

In this lesson we'll create a protected route just for logged in users. We'll combine a Route with a render prop and use a loggedIn prop to determine if the route should be allowed to be accessed. Finally we'll use nav state to preserve the location the user visited and redirect them back to the protected route once they login.

Create a ProtectedRoute Component in React Router

In this lesson we'll use the `matchPath` function exported by react-router to find active nested routes inside of a parent component. This technique can be used for comparing routes outside of a React component, or even inside of life cycle methods to do data loading.

Use matchPath to Match Nested Route Paths in Parent Routes with React-Router

In this lesson we'll explore how to test that an async form submission successfully happened using Jest. We'll also take advantage of react-testing-library to render our react components to a fake dom. We'll use `MemoryRouter` to mock what a browser would normally do in the event of a transition, and create a fake component route to confirm that the submission successfully redirected us to the url we wanted.

Test Successful Async Form Submissions with React Router

In this lesson you will learn how to attach Event Handlers to buttons and input fields. Event handlers normally follows the `on:[event]` format. If you are making use of two way binding you should use `bind:` instead, for example an input field could use bind:value.

Use Event Handlers in Svelte 2

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.