Learn Eslint, Nginx and Rails

The pluggable linting utility for JavaScript and JSX.

eslint

One of the other tools I use is Emmet. It's used for writing HTML much more quickly by using shorthand. It can also be used for JSX. VSCode also supports ESLint which we will use and configure in our VSCode `settings.json`. I will also set up Prettier as my default formatter for TypeScript and TypeScript React files. 

Configure Emmet, ESlint, and Prettier Extensions

We can leverage GitHub Actions to automate the running of all of our accessibility auditing tools as part of a Continuous Integration (CI) workflow. 

Auditing tools will only catch a percentage of potential accessibility issues, it is no replacement for manual testing.  But being able to automate the auditing will add efficiencies to our testing and provide an early warning system that can be run much more frequently than it’s practical to perform manual testing.  Additionally, we can use our CI suite as a safety net to prevent code changes that break accessibility from being able to be merged.

## Resources
* https://app.egghead.io/lessons/react-set-up-eslint-to-audit-accessibility-issues-in-react
* https://docs.cypress.io/guides/continuous-integration/github-actions#Basic-Setup
* https://github.com/cypress-io/github-action

Automate Accessibility Audits with GitHub Actions

Node.js is a platform built on Chrome's JavaScript runtime for easily building fast, scalable network applications. Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient, perfect for data-intensive real-time applications that run across distributed devices.

node

Ghost has two hard dependencies which need to be installed before it can run. Those are Nginx and Node.js.

We will start by installing Nginx and set Nginx up to control the traffic coming into the EC2 server. After this, we'll install NVM using the raw install script that they provide on GitHub. With NVM installed we can then install the latest version of Node.js


Install Nginx and Node.js on a AWS EC2 Server

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

Nx already comes with a default TypeScript setup. Although you can opt-out of that and generate plain JS based components, especially in a large setup TypeScript can be beneficial in uncovering potential issues early. To add an extra level, Nx also comes with preconfigured eslint for all the apps and libraries. In this lesson we're going to explore the lint setup and how it can be used.

Linting a React app with Nx

Rails is a web-application framework that includes everything needed to create database-backed web applications according to the Model-View-Controller (MVC) pattern.

rails

When you create a User model with Devise using the command `rails generate devise User`. Devise will create  default columns in the database for your User model. To add your own columns for your users you can create a new Rails migration and add any columns you want for your users.

Add Custom Fields to a Devise User Model with a Ruby on Rails Migration

If you want to give the users the ability to follow or become friends with each other. Rails lets you create a join table in your database and have it reference the user database table. 

You can use Active Record to associate the new table with User table by using the `class_name` method

Create Active Record Self-Referential Relationships In Ruby on Rails

If you make a mistake when naming your database column, and have data that you want to keep unchanged. You can use the change method with the rename_column definition in your migrations files to update a single column name in your database.

Rename A Database Column with Ruby on Rails Active Record Migrations

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

In this lesson you will learn how to use the eslint yeoman generator to scaffold a new plugin to provide custom rules for your project. 
You will also be able to check the basic skeleton for an eslint ruleand a working example rule to apply a naming convention for async functions.

Scaffold an eslint Plugin with Yeoman

We have a number of options to use when testing for accessibility issues concerning alternative text for images.  The react-axe library and axe browser extension will both report when an image is missing alternative text.  The tota11y browser extension will annotate any images that are missing alternative text.  Running eslint with the eslint-plugin-jsx-a11y plugin installed will report on any `<img>` elements missing an `alt` attribute.  Finally, we can use a screen reader to actually hear what is read when an image has focus.

Test for Image Alternative Text Accessibility Issues

Images must have text alternatives that describe the information or function 
represented by them so they can be read and understood by those using screen readers.

## Alternative text for images
* All `<img>` elements should have an `alt` attribute provided
    * When not provided many screen readers will fallback to reading the file name instead
* The `alt` value should not include words like _“image”_, _“picture”_ or _“icon”_
    * Screen readers are already announcing that the element is an image
* Images that are decorative only and provide no information or function to the page should be hidden from Assistive Technologies by providing an empty `alt` attribute (`alt=””`)

## References
* https://www.w3.org/WAI/tutorials/images/
* https://www.w3.org/WAI/tutorials/images/decision-tree/
* https://www.w3.org/WAI/tutorials/images/tips/
* https://www.w3.org/WAI/tutorials/images/informative/
* https://www.w3.org/WAI/tutorials/images/functional/
* https://www.w3.org/WAI/tutorials/images/textual/

Define Images with Appropriate Text Alternatives

Our accessibility auditing toolkit makes it very easy for us to test for any form controls that are missing labels or are not correctly associated with their labels.  Running Eslint with the eslint-plugin-jsx-a11y installed will show us any form controls with missing or unassociated labels.  Running react-axe or using axe to audit a web page will similarly list any of these findings.  Finally using tota11y we can annotate any form controls on a page that are missing labels.  This is definitely some of the lower hanging fruit that we can easily find and fix when making our applications accessible!

Test for Form Control Label Accessibility Issues

Labeling inputs, elements, and widgets add context and clarity for assistive technology such as screen readers.  Elements of a `<form>` such as `<input>` or `<textarea>` or `<select>` should be labelled by using a `<label>` element.  Placeholder text can be used in addition to a label but should not be used in place of a label as not all assistive technologies respect placeholder text.

Ensure Form Controls have Accessible Labels

Our first layer of defense when building accessible React applications is to add some auditing tools to our development workflow. This should include adding static analysis checking for common accessibility standards and best practices. We can get this with the latest eslint plugin: "eslint-plugin-jsx-a11y". If you are already linting your projects adding this plugin should fit very smoothly into your workflow.

## Resources
1. [List of all the rules supported by eslint-plugin-jsx-a11y](https://github.com/evcohen/eslint-plugin-jsx-a11y#supported-rules)
2. [Comparison of the difference in rules between recommended and strict mode](https://github.com/evcohen/eslint-plugin-jsx-a11y#difference-between-recommended-and-strict-mode)
3. [Background on how the Accessibility API implemented by browsers interfaces with Assistive Technologies](https://github.com/evcohen/eslint-plugin-jsx-a11y#some-background-on-wai-aria-the-ax-tree-and-browsers)

Set up ESLint to Audit Accessibility Issues in React

Learn how to test custom ActiveRecord validations using RSpec.

In this lesson we'll write a test that expects the `email` to be found on the `invitations` table. We'll see that at first this test fails because we need to add the custom validation on the user model. Once we implement the validation and create the `InvitedValidator`, the test will pass.

Test Custom ActiveRecord Validations

Learn how to test ActiveRecord validations using RSpec.

In this lesson we'll write a test that expects the `name` attribute to be present on the User model instance. We'll see that at first this test fails because we need to add this validation on the model.

Test ActiveRecord Validations

Learn how to test ActiveRecord named scopes using RSpec.

In this lesson, we will test a `User` model that will have a `by_ci_email` method 
that we will define on the model. We will test this method in our `user_spec.rb` file and pass in a lower case email argument to demonstrate that the `by_ci_email` method is functioning correctly by finding the correct user.

Test ActiveRecord Named Scopes

JavaScript is great! JavaScript is also full of features and flexible options that can make it easy to introduce bugs. ESLint uses static analysis to check that your code adheres to a list of rules to help you avoid some specific runtime errors. ESLint is highly configurable, so in this lesson, we'll install ESLint and configure some baseline rules for our boilerplate.

Avoid Common JavaScript Errors with ESLint 

NGINX is a free, open-source, high-performance HTTP server and reverse proxy, as well as an IMAP/POP3 proxy server. 

nginx

Node.js apps built with Docker cannot scale horizontally by themselves. In this lesson we will spawn out multiple Node.js processes/containers, and move the incoming request handler to an Nginx proxy to load balance and properly scale our Node.js app.

Scale Docker Horizontally with Nginx Load Balancing

Learn how to setup an Nginx proxy server with Docker that sits in front of a Node.js app. You can use a proxy to control the flow of frontend requests hitting your app, as well as to achieve better performance and scalability. We'll create a sample Node.js app, configure a default Nginx configuration file for proxying web requests, build both Node.js and Nginx Docker images, and learn how to link everything up and get it running with Docker specifics.

Setup an Nginx Proxy for a Node.js App with Docker

Learn about the concepts of managing data within Docker volumes, including all of the commands to create and manage volumes. We'll demonstrate how to mount a Docker volume to one or many containers by creating and mounting a volume to an Nginx proxy, and then verify the output with curl. You'll also see how changes to files within volumes of one container propagate to other containers with the same volume mounted, and learn various commands to inspect Docker volumes.

Manage Data within Docker Volumes

Nuclide is the IDE Facebook employees use to write React code. But setting it up to use Flow type checking and Eslint to lint files on the fly is tricky. This video shows you how. 

Setup Nuclide to use Flow and Eslint (Mac)



Discover how to harness the power of Cursor IDE's Composer Agent feature to optimize your code. In this lesson, you'll witness an AI agent doing all the work to generate test suites, implement performance benchmarks, and create optimized function variations - all without writing a single line of code. You'll learn how to validate performance improvements through data-driven benchmarking, ensuring that optimizations are backed by concrete metrics rather than speculation. This hands-on demonstration showcases a groundbreaking approach to automated function development that combines the precision of test-driven development with the efficiency of AI-powered optimization.


Agent-Driven Development in Cursor: Testing, Benchmarking, and Optimizing Functions

This course is aimed for using `zod` effectively in projects based on TypeScript (both browser and node.js). The benefits you gain with this course is not just simply coding, but also understanding when/why/how should you perform runtime validation.

`zod` is the missing piece to TypeScript's capabilities, which can guarantee type-safety only in compile-time.

`zod` can be used whenever the compiler cannot guarantee what happens in runtime. And... it's a very frequent usecase, such as HTTP calls, websockets, etc.

In this course you get quickly up and running by:
1. using `zod` with primitives and objects
2. adapting `zod` quickly to existing projects thanks to automatic generators
3. changing the strategy frm type-first to schema-first
4. using error-throwing `parse` or non-error-throwing `safeParse` basing on your needs
5. applying `zod` to the most common usecase - validating API responses
6. handling errors the most convenient way (out of many!)

Take advantage of runtime validation with `zod`. Take advantage of the detailed lessons in this course 🔥

Effective Runtime Type Checks with Zod


Cursor can now automatically run commands in the terminal and walk step-by-step towards building out your entire project. You give it a goal, then it will suggest the commands you need to run and the files that you need to create and you can work with it to achieve what you're building. This lesson does a quick walkthough of using a Cursor Agent to build a project from scratch and guide it along the way. Cursor Agents definitely feel like a sneak peek at the future of programming!

Cursor Agents Initial Impressions - Allow an AI to Build Your Entire Project

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


While using anonymous functions might seem convenient, they can create difficulties when trying to identify performance bottlenecks during profiling. This lesson will demonstrate how named functions make it easier to pinpoint and address performance issues, ultimately leading to more efficient and debuggable code. Learning this practice will greatly improve your ability to locate and fix performance issues in complex projects.

Always Name Functions in JavaScript


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

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