 Courses from John Otander

[Theme UI](https://theme-ui.com) is a library created by [Brent Jackson](https://jxnblk.com) for building themeable React apps with [Gatsby](https://gatsbyjs.org). It's built with [Styled System](https://styled-system.com) which provides a constrained set of styling APIs based on props. It uses [Emotion](https://emotion.sh) and [MDX](https://mdxjs.com) underneath which abstracts us away from a lot of the challenges when dealing with global CSS and styling content.

Theme UI uses ["presentational context"](https://johno.com/presentational-context) to allow a component to apply styling to child elements without introducing global styles. You can use a styles object in your configuration to apply theme-aware styles to ensure consistency.

Bite-size video tutorials for badass web developers.

egghead

Theme UI

[unified](https://unifiedjs.com) enables new exciting projects like [Gatsby](https://gatsbyjs.org) to pull in Markdown, [MDX](https://mdxjs.com) to embed JSX, and [Prettier](https://prettier.io) to format it. It’s used in about 300k projects on GitHub and has about 10m downloads each month on npm.

unified uses abstract syntax trees, or ASTs, that plugins can operate on. It can even process between different formats. This means you can parse a markdown document, transform it to HTML, and then transpile back to markdown.

unified leverages a syntax tree specification (called unist or UST) so that utilities can be shared amongst different formats. In practice, you can use unist-util-visit to visit nodes using the same library with the same API on any supported AST.

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

unified - the compiler for your content

[remark](https://github.com/remarkjs/remark) is a pluggable markdown parser and compiler. It's part of the [unified](https://unifiedjs.com) so it offers a wide array of libraries to make writing plugins with the markdown AST ([MDAST](https://github.com/syntax-tree/mdast)) more developer friendly.

We'll use `unist-util-visit` to traverse heading nodes in a Markdown file and prefix all `h1`s with the text "BREAKING" using a TDD workflow.

Create a remark Plugin to Modify Markdown Headings

Most of the time with markdown documents we want to render them to HTML for static websites. You can use remark and the [remark-html](https://github.com/remarkjs/remark-html) plugin to transpile your markdown documents to HTML with a build script.

Convert Markdown to HTML with remark-html

Manually maintaining a table of contents in markdown documents can be a lot of work. By combining [remark-toc](https://github.com/remarkjs/remark-toc) and [remark-slug](https://github.com/remarkjs/remark-toc) you can ensure generate your table of contents and ensure it's always up to date.

Add a Dynamic Table of Contents to Your Markdown Documents with remark-toc

When using remark to manipulate markdown documents, you can use [unist-util-remove](https://www.npmjs.com/package/unist-util-remove) to remove nodes of a particular type. You can combine it with [unist-util-visit](https://www.npmjs.com/package/unist-util-remove) to remove nodes based on their parent's context in the AST.

In this example, we remove all images contained within heading nodes.

Remove Markdown Nodes from a Document with unist-util-remove

[PostCSS](https://github.com/postcss/postcss) is a CSS processor that allows you to modify source CSS with plugins. In this lesson we'll modify the CSS AST by creating a plugin that removes declarations when they contain vendor prefixes.

Create a PostCSS Plugin to Remove Vendor Prefixes

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

When you use a component for your table of contents in MDX documents you have more flexibility around how you render it. In this lesson, we'll use Gatsby's GraphQL data layer to fetch the headings in an MDX document and pass them to a TableOfContents component that we create.

Create a Table of Contents Component for MDX Documents in Gatsby

You can use the remark CLI to inspect the AST, run plugins, or lint your markdown documents. It can be used in your build scripts to generate HTML or ensure your markdown style guide is adhered to.

- Inspect the AST: `remark document.md --inspect`
- Use a plugin: `remark document.md --use toc`
- Overwrite your document after the plugin runs: `remark document.md --use toc -o`
- Lint a document: `remark document.md --frail --use preset-lint-markdown-style-guide`

Introduction to the remark CLI

[regexr](https://regexr.com) is a powerful tool for debugging existing regexes and creating new ones. In this lesson, we'll use the app to create a regex that matches Twitter-style mentions in a string. It will go over a few regex concepts including capture groups, character sets, and flags.

Construct a Regex to Match Twitter Mentions with Regexr

Cascading Style Sheets bring order and beauty to our applications.

You can use the background-clip CSS property to create text gradients that are made up of selectable text. This approach can be used with background images as well.

```css
h1 {
  font-size: 100px;
  background-image: linear-gradient(300deg, tomato 25%, red 80%);
  background-clip: text;
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}
```

Create a Text Gradient in CSS with Background Clip

You can use unified's [virtual file](https://github.com/vfile) to add data from a document in order to use it elsewhere. In this lesson we'll store metadata from all heading nodes in a markdown document using remark and vfile.

Store Heading Metadata in a Markdown Document with remark

[Theme UI](https://theme-ui.com) provides a wrapper around the MDXProvider so you can add styling to components that are rendered in your MDX documents. The styling you add will not be leaked as global styles since it relies on React Context and Emotion. The values set in the `styles` object are [theme-aware](https://theme-ui.com/theming) so you can ensure consistency when applying color and typographic styles to your content.

This lesson uses `gatsby-plugin-theme-ui` in order to seamlessly integrate Theme UI into a Gatsby site.

Style Components Rendered By MDX with Theme UI in Gatsby

If you want to offer more than two color modes in your Theme UI-based site you can create a button that can activate all color modes. In this lesson we'll add two new color modes, for a total of four, and then use the `useThemeUI` hook to create an array of color modes to cycle through.

Cycle Through Multiple Theme UI Color Modes

Gatsby is a blazing fast static site generator built with React. Gatsby gives you all of the modern JavaScript tools you want; set up and ready to go out of the box.

gatsby

[Theme UI](https://theme-ui.com) is a library created by [Brent Jackson](https://jxnblk.com) for building themeable React apps with [Gatsby](https://gatsbyjs.org). It's built with [Styled System](https://styled-system.com) which provides a constrained set of styling APIs based on props. It uses [Emotion](https://emotion.sh) underneath which abstracts us away from a lot of the challenges when dealing with global CSS.

Theme UI uses ["presentational context"](https://johno.com/presentational-context) to allow a component to apply styling to child elements without introducing global styles. You can use a `styles` object in your configuration to apply theme-aware styles to ensure consistency.

Introduction to Theme UI

Theme UI has a collection of [presets](https://theme-ui.com/presets) you can import into your app and even extend. In this lesson we'll replace an existing theme file with a preset and then extend it.

Use and Modify a Theme UI Preset

Theme UI has built-in [color mode support](https://theme-ui.com/color-modes/) that makes it straightforward to add a dark mode to your Gatsby project. You can use the `useColorMode` hook to retrieve the active color palette and set it to a predefined dark color palette.

John Otander

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