Learn Cloudflare, Jest and Scss

Cloudflare Workers let you write JavaScript Service Workers that run directly in Cloudflare's 200+ edge locations around the world.

With a Cloudflare Worker, you can modify your site's HTTP requests and responses, make parallel requests, and even reply directly from the edge.

Cloudflare Workers are written against a similar API to the W3C Service Workers standard. However, while Service Workers run inside the end user's browser, Cloudflare Workers run on Cloudflare's servers. This means that Cloudflare Workers can implement trusted code (which the client cannot tamper with), and will work no matter what browser the user is running.

In this course, Kristian Freeman will teach you how to build and deploy a Serverless API with Cloudflare Workers. By learning how to build your own serverless JSON APIs, you can effectively manage a highly-available backend for your projects, without needing to learn DevOps or manage services.

Cloudflare secures and ensures the reliability of your external-facing resources such as websites, APIs, and applications. It protects your internal resources such as behind-the-firewall applications, teams, and devices. And it is your platform for developing globally-scalable applications.

cloudflare

Build a Serverless API with Cloudflare Workers

It's tempting to pick up a framework which has preselected flexbox or grid as the layout tool of choice, but it's important to learn when and why to use each method. This leads to slimmer stylesheets which results in better site performance, and less likelihood for "hacks" to make one method do what the other does inherently better. 

Throughout this collection, we will be progressively styling a responsive landing page template while building your knowledge on when to select grid or flexbox for any layout scenario. Spoiler alert: sometimes the best solution is using both!

The specification describes a CSS box model optimized for user interface design. In the flex layout model, the children of a flex container can be laid out in any direction, and can “flex” their sizes, either growing to fill unused space or shrinking to avoid overflowing the parent.

flexbox

Create a Landing Page with CSS Grid and Flexbox

Cloudflare Workers is a serverless application platform that enables you to create and deploy functions to Cloudflare's Edge Network.

Unlike other serverless providers that only have regional data centers, Cloudflare's Edge Network consists of hundreds of servers all over the world.

Cloudflare Workers is a powerful platform, and this course serves as a great introduction for what it can do.

Follow along with Kristian Freeman as you build a localization engine that renders data based on the Edge location nearest to the application's user.

After this course, you'll be ready to start experimenting with your own Cloudflare Workers projects. *Need an idea?* *[Check out the suggested Portfolio Project for this course.](https://egghead.io/projects/introduction-to-cloudflare-workers)*

Introduction to Cloudflare Workers

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

The “Edge” is where you write and store your code where your data is being produced. This allows for a quick and efficient data transfer, eliminating or severely reducing lag. 

Supabase is a suite of open-source tools wrapping a PostgreSQL database. It provides the building blocks of an app - database hosting, auth, file storage, real-time, and edge functions - so we can focus on what makes our app unique.

Cloudflare Workers are serverless functions that run at the Edge! In this course, we will use the Wrangler CLI tool for interfacing with your Cloudflare account and creating or publishing your Workers.

KV Storage is a cache that Cloudflare makes available to our Workers. It replicates across multiple CDN nodes, making it super performant to cache data.

Combined, these three things give you the benefits of that reduced lag in a smooth and streamlined process. 

Throughout this course, Jon will teach you how to create a small blog that hits the key points of how to:

- Query Supabase from Cloudflare Workers
- Read and write KV Storage cache from Cloudflare Worker
- Cache Supabase response at the Edge with KV storage

And more! 

Cache Supabase data at the Edge with Cloudflare Workers and KV Storage

CSS uses a global namespace for CSS Selectors that can easily result in style conflicts throughout your application when building an application using modern web components. You can avoid this problem by nesting CSS selectors or use a styling convention like BEM but this becomes complicated quickly and won’t scale.

CSS-in-JS avoids these problems entirely by generating unique class names when styles are converted to CSS. This allows you to think about styles on a component level with out worrying about styles defined elsewhere.

In this course, you will learn how to express popular SCSS (Sass) language features using latest JavaScript features. We will convert simple examples from SCSS to CSS-in-JS. As a designer or (S)CSS developer, you should be able to follow without extensive JavaScript knowledge, understanding SCSS is required though. We will not be using any particular CSSinJS libraries. Instead, we will focus on a base knowledge you need later if you use any CSSinJS library.

Sass is the most mature, stable, and powerful professional grade CSS extension language in the world.

scss

Convert SCSS (Sass) to CSS-in-JS

Have you ever wished for access to conditionals or iteration when writing styles? How cool would it be to use functions to write styles? SCSS has that and more! SCSS is a superset of CSS. Any valid CSS is SCSS, they even have the same syntax. SCSS borrows features from other languages to write smarter, reusable and more readable styles. This course will focus on how to use SCSS’s more useful features, compare them against each other and assess when their usage is appropriate.

Learn the Best and Most Useful SCSS

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

The Edge is one of the most exciting new topics in web development. At the front of the pack is Cloudflare, whose network boasts servers located in hundreds of cities all over the world instead of in regions like "East" or "West".

More servers in more locations mean a faster experience for your users.

But what about the data part of the equation?

If the application you're working on skews more toward "reading" rather than "writing" data, Cloudflare Workers KV is a perfect fit.

Once you create a KV namespace— the "KV" stands for "key-value"— Cloudflare keeps track of your application data. The most commonly accessed data will be propagated around the world to the various Edge servers, while less popular data will be stored in more central locations.

Kristian Freeman has produced courses that introduce how to build and deploy sites and JSON APIs powered by Cloudflare Workers.

Today, he will show you how Workers KV can be integrated into a Cloudflare Workers project through building a Todo App.

## The Project

![todo-app-screenshot](https://res.cloudinary.com/dg3gyk0gu/image/upload/v1639014074/course-resources/Build-data-driven-applications-on-the-edge-with-Workers-and-Workers-KV/CleanShot_2021-12-08_at_16.46.39_2x.png)

Before you groan about a bland Todo App, think about it this way: 

The Todo App is the perfect example of the CRUD operations. Cloudflare KV has its own nuances for reading and writing data through a concept called Binding that is easier to grok when you understand the larger example as a whole.

As the course progresses, Kristian shares examples of how you can store more complex key-values, along with data operations like editing and filtering.

One of the coolest features that Cloudflare KV allows for is user-specific data that is tied to the IP address the request originates from. In other words, you'll be able to share your deployed Todo app with anyone around the world, and they will only see their personal items.

## **Gain these Skills**

- Manipulating data using Cloudflare Workers KV
- Make data unique to each user without logging in
- Effectively store lightweight data in Cloudflare Workers KV
- Setting up a key-value store and connected projects
- Reading and writing to a serverless key-value store
- Storing complex values in a Cloudflare KV store

## **Prerequisites**

You'll need to have a basic understanding of what Cloudflare Workers is recommended but not necessary. This course is relatively beginner-friendly into the world of Workers KV that you can get by with no knowledge on Cloudflare Workers. 

But if you want to get the most out of this course, we would recommend taking [Introduction to Cloudflare Workers](https://egghead.io/courses/introduction-to-cloudflare-workers-5aa3) to get a better understanding of how Workers KV comes into play. 

## **What's Next? (You might also like these resources:)**

Follow along with Kristian Freeman as you build a localization engine that renders data based on the Edge location nearest to the application's user. → [Introduction to Cloudflare Workers](https://egghead.io/courses/introduction-to-cloudflare-workers-5aa3) 

Learn how to build your own serverless APIs so you can manage a highly available backend for your projects. No Learning DevOps or managing services necessary. →  [Build a Serverless API with Cloudflare Workers](https://egghead.io/courses/build-a-serverless-api-with-cloudflare-workers-d67ca551)

Using Cloudflare Pages and Cloudflare Workers, it's easy to create dynamic front ends that you can deploy in just seconds from GitHub. → [Deploy Dynamic Frontend Applications with Cloudflare Pages](https://egghead.io/courses/deploy-dynamic-frontend-applications-with-cloudflare-pages-6aaa00a1)

Build Data-Driven Applications on the Edge with Workers and Workers KV

Techniques to improve your CSS, Sass, and HTML implementations for everyday scenarios. 

Learn the Fundamentals of CSS and Sass to Create Modern and Responsive Layouts 

Copy/pasting the same code is redundant and updating copy/pasted code slows development velocity. Mixins are reusable chunks of code that are included, similar to calling a function, instead of copy/pasted.

Mixins have some nice features:
- Arguments just like functions.
- Arguments can have default values and optional values.
- Named arguments allow us to use optional and default arguments when the mixin is included.
- Variable arguments allow us to have a dynamic number of arguments when the mixin is included.
- The @content directive allow us to add additional styles when the mixin is included.

In this lesson we learn how to DRY up the code with the SCSS @mixin directive and make copy/paste a thing of the past.

Reuse Styles with the SCSS @mixin Directive

Updating the same color or metric multiple times is no fun. SCSS variables improve maintainability by allowing one name to represent a value that can be used anywhere. SCSS variables also give us the power of creating our own naming conventions to express the intent of specific values. In this lesson we learn how to use SCSS variables to assign user friendly names to colors/metrics so one value change will update that value in all the right places.

Use SCSS Variables for Readable and Maintainable Stylesheets

SCSS nesting can produce DRYer code by targeting child elements without having to write the parent class. Nesting up to 3 levels deep can help us understand relationships between styles. The SCSS parent selector represents the parent class, so it can DRY up targeting pseudo-elements/classes and be an asset for naming conventions. In this lesson we learn how to remove the redundancy of targeting pseudo-elements/classes, and child elements by taking advantage of SCSS’s nesting and parent selectors.

Organize Styles with SCSS Nesting and the Parent Selector

In this lesson we learn how to set up SCSS  and transpile your SCSS code into CSS with node-sass.

Transpile SCSS to CSS using node-sass

Tired of dealing with monolithic CSS files? Are requests for multiple CSS files hurting your performance? In this lesson we learn how to separate our styles with SCSS partials, and how SCSS imports compile to one file so there's only one request.

Organize SCSS into Multiple Files with Partials

We can write reusable styles with the SCSS @extend or @mixin directives. Which one is better? It depends. A better question is, how do they differ?
Extends:
change the source order, mixins don’t.
maintain relationships, mixins don’t.
share inherited traits, mixins don’t.
can extend multiple classes, mixins don’t.
can create multiple class declarations in the compiled CSS, mixins don’t.
can use the placeholder selector, mixins don’t.

Mixins:
can accept arguments, extends don’t.
can pass additional content, extends don’t.
repeat code when compiled, extends group class names together.
work well wIth media queries, extends have a limited interaction wIth media queries.

In this lesson we learn about writing reusable styles with the @extend directive and how it compares to the @mixin directive.


Reuse Styles with the SCSS @extend Directive

Writing similar classes with minor variations, like utility classes, can be a pain to write and update. Sometimes just a single character is the only difference between classes and updating the defining parameter means we need to change it for every class name and value. We can write a class one time and the @for directive can write all the minor variations for us. If the similar classes need to be updated, with the help of the @for directive, they only need to be updated once. In this lesson we learn how to leverage the power of the SCSS @for control directive to relieve the pain.

Write similar classes with the SCSS @for Control Directive

The SCSS @for directive is great when we know how many iterations are required and we only need 1 variable. What if we need multiple variables to iterate over data sets? Hello SCSS maps and the @each control directive! In this lesson, we’ll check out iterating with lists and looping over data sets with maps and the @each directive.

Loop Over Data with the SCSS @each Control Directive

Writing SCSS @functions is similar to writing functions in other programming languages; they can accept arguments and have return statements. SCSS provides a ton of great features, but sometimes we need to roll our own function. We can do that too! They’re useful when the desired functionality isn’t available from the built in SCSS functions and a mixin just won’t do. In this lesson, we learn how and when to use SCSS function directives.


Write Custom Functions with the SCSS @function Directive

We can use javascript for color and opacity variations, math, list and map logic or to see if something exists. SCSS includes functions for a wide range of common use cases for logic in our styles. In this lesson we look at some of the more useful color functions to improve development velocity, readability, and simplify the code. Be sure to checkout all the SCSS functions: http://sass-lang.com/documentation/Sass/Script/Functions.html

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