Learn Eslint, Scss and Xstream

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

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

Cascading Style Sheets bring order and beauty to our applications.

In this lesson we'll learn how to convert our Sass code to CSS code. We'll take a look at the sass watch command and use it to listen for changes within our Sass code.

The `sass` executable can be downloaded globally through npm by running `npm i -g sass`.

Converting Sass To CSS

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

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

The pluggable linting utility for JavaScript and JSX.

eslint

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

Manage the color palette used in your stylesheets by creating a map of variables and a function to access the values by key. This allows you to update the colors in one location to re-theme your application and eliminate manual find and replace.

Access Theme Color Values With Sass

Learn the fundamental difference between CSS grid and flexbox layout, and create utility classes for each `display` value. Then begin to apply and expand these concepts to style the landing page navigation.

Choose Between Grid or Flexbox for CSS Layout

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

Apply grid layout and see when it's necessary to break out a media query to overcome grid's lack of wrapping behavior. We'll also learn about a property that grid and flexbox share: `align-items`.

Use CSS Grid to Create Layout Columns

Grid offers us the easiest method to responsively center content. We'll use the grid property `place-content` to center the contents of `figure` to showcase our fictional product in use. Additionally, we'll learn about `object-fit` which is a modern technique that allows inline images to scale responsively within defined dimensions without distortion.

Responsively Center an Image and Caption with CSS Grid

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

We'll define the color palette and create the basic screen styles for our project in addition to Sass helpers for our form design system. 

We will set up Sass variables for the initial them and learn how to use the !default flag to allow our system to be easily overridden from project to project, making our form styles ultra transferable and reusable. You'll also learn how to leverage Sass color functions for ease of theming. We'll map the Sass variables to CSS variables so that as we build up our system we can use CSS variables for the most flexibility in our theming.

Initialize the Form Design System Setup with Sass and CSS Variables

View a preview of the form fields we'll be creating in this course, inclusive of custom CSS styles for text inputs, textareas, selects, multiselects, radio buttons, and checkboxes. Then get an overview of the base project and key parts of the Eleventy build process in regards to compiling with Dart Sass and use of Nunjucks for project template scaffolding. 

Prior experience with Eleventy or Nunjucks is not required, but you may also enjoy learning how to [create an Eleventy site from scratch](https://egghead.io/playlists/build-an-eleventy-11ty-site-from-scratch-bfd3?af=2s65ms) in less than 20 mins in my other egghead collection.

Course Introduction: Accessible Cross-Browser Form Field CSS Styles

We'll make a starting point for our form layout styles by creating `.form-group` which will add a bit of `margin` between fields. This will be our first design system component, and we'll also include styles for the `label` contained in this class.

Create the `form-group` Component Styles

Learn how to begin addressing browser inconsistencies by resetting base styles across text inputs, textareas, and selects. We'll also review a few quirks related to mobile browsers and responsive design when dealing with form fields. And we'll uncover how to normalize `<select>` which was formerly one of the trickiest fields but is vastly easier now thanks to modern CSS through the `appearance` property.

Create Reset Styles to Normalize Form Fields Cross-Browser

We'll begin to apply our theme styles for our text inputs by creating the `.form-field` component. We'll make use of the Sass feature of "mixins" to create `:focus` and `:disabled` styles that can be reused. While creating the `:focus` and `:disabled` states we'll discuss the importance of contrast and keyboard access for accessibility.

An important take-away is that you need at least a 3:1 contrast ratio between your border and background AS WELL AS a 3:1 contrast ratio between your border and focus state.

Use Sass Mixins to Style Inputs with Accessible Contrast and Keyboard Access

Using modern CSS and in particular CSS grid and `clip-path` we can define cross-browser compatible custom select CSS styles inclusive of the dropdown arrow. We'll continue ensuring all styles are re-themeable by using the Sass functions we've already created within our form design system. We will style both the default single select, and a multi-select using `multiple`.

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