# hubdown [![CircleCI build status](https://circleci.com/gh/electron/hubdown/tree/master.svg?style=svg)](https://circleci.com/gh/electron/hubdown/tree/master) > Convert markdown to GitHub-style HTML using a common set of [remark] and [rehype] plugins Used by [electron/i18n](https://github.com/electron/i18n) and [electronjs.org](https://github.com/electron/electronjs.org). [unified] processes content with syntax trees and transforms between different formats. [remark] and [rehype] are its markdown and HTML ecosystems. We use this because its performant and has a large collection of plugins. Primarily, unlike some other node markdown parsers that provide syntax highlighting capabilities, unified does not have any native C++ dependencies. This makes it easier to install and reduces the likelihood of system-dependent installation failures. ## Plugins The following [remark] and [rehype] plugins are used by hubdown: - [remark-parse](http://ghub.io/remark-parse) parses markdown - [remark-gemoji-to-emoji](http://ghub.io/remark-gemoji-to-emoji) transforms gemoji shortcodes to emoji - [remark-rehype](http://ghub.io/remark-rehype) transforms markdown to HTML - [rehype-slug](http://ghub.io/rehype-slug) adds DOM ids to headings - [rehype-autolink-headings](http://ghub.io/rehype-autolink-headings) turns headings into links - [rehype-highlight.js](http://ghub.io/rehype-highlight) applies syntax highlighting to code blocks using highlight.js (supports the [default languages](https://github.com/highlightjs/highlight.js/blob/master/SUPPORTED_LANGUAGES.md) as well as [GraphQL](https://github.com/dpeek/highlightjs-graphql)) - [rehype-stringify](http://ghub.io/rehype-stringify) stringifies HTML ## Installation ```sh npm install hubdown --save ``` ## Usage hubdown exports a single function that returns a promise: ```js const hubdown = require('hubdown') hubdown('I am markdown').then(doc => { console.log(doc) }) ``` The resolved promise yields an object with a `content` property containing the parsed HTML: ```js { content: '

I am markdown

' } ``` ## Usage with Cache hubdown's `remark` markdown parser is pretty fast, but things can start to slow down when you're processing hundreds or thousands of files. To make life easier in these situations you can use hubdown's optional cache, which stores preprocessed markdown for fast retrieval on subsequent runs. To use the cache, bring your own [level](https://ghub.io/level) instance and supply it as an option to hubdown. This helps keep hubdown lean on (native) dependencies for users who don't need the cache. ```js const hubdown = require('hubdown') const cache = require('level')('./my-hubdown-cache') hubdown('I will be cached.', { cache }).then(doc => { console.log(doc) }) ``` ## API ### `hubdown(markdownString[, options])` Arguments: - `markdownString` String - (required) - `options` Object - (optional) - `runBefore` Array of [remark] plugins - Custom plugins to be run before the commonly used plugins listed [above](#plugins). - `frontmatter` Boolean - Whether or not to try to parse [YML frontmatter] in the file. Defaults to `false`. - `cache` [LevelDB](https://ghub.io/level) - An optional `level` instance in which to store preprocessed content. See [Usage with Cache](#usage-with-cache). - `highlight` - Object of [rehype-highlight](https://github.com/rehypejs/rehype-highlighthighlight#options) options. Returns a promise. The resolved object looks like this: ```js { content: 'HTML goes here' } ``` If [YML frontmatter] is parsed, those properties will be present on the object too: ```js { title: 'The Feminine Mystique', author: 'Betty Friedan', content: '

The Feminine Mystique is a book written by Betty Friedan which is widely credited with sparking the beginning of second-wave feminism in the United States.

' } ``` ## Tests ```sh npm install npm test ``` ## License MIT [unified]: http://ghub.io/unified [remark]: http://ghub.io/remark [rehype]: http://ghub.io/rehype [YML frontmatter]: https://jekyllrb.com/docs/frontmatter