Documentation is one of your product's interfaces with your users. A well-written and well-organized set of docs helps your users understand your product quickly. Our aligned goal here is to help your users find and understand the information they need, as quickly as possible.
Docusaurus 2 uses modern tooling to help you compose your interactive documentations with ease. You may embed React components, or build live coding blocks where your users may play with the code on the spot. Start sharing your eureka moments with the code your audience cannot walk away from. It is perhaps the most effective way of attracting potential users.
In this section, we'd like to introduce you to the tools we've picked that we believe will help you build powerful documentation. Let us walk you through with an example.
Markdown is a syntax that enables you to write formatted content in a readable syntax. The [standard Markdown syntax](https://daringfireball.net/projects/markdown/syntax) is supported and we use [MDX](https://mdxjs.com/) as the parsing engine, which can do much more than just parsing Markdown. More on that later.
- `sidebar_label`: The text shown in the document sidebar and in the next/previous button for this document. If this field is not present, the document's `sidebar_label` will default to its `title`.
- `custom_edit_url`: The URL for editing this document. If this field is not present, the document's edit URL will fall back to `editUrl` from options fields passed to `docusaurus-plugin-content-docs`.
- `description`: The description of your document, which will become the `<meta name="description" content="..."/>` and `<meta property="og:description" content="..."/>` in `<head>`, used by search engines. If this field is not present, it will default to the first line of the contents.
If you want to reference another document file, you could use the name of the document you want to reference. Docusaurus will convert the file path to be the final website path (and remove the `.md`).
Docusaurus has built-in support for [MDX](https://mdxjs.com/), which allows you to write JSX within your Markdown files and render them as React components.
**Note 1:** While both `.md` and `.mdx` files are parsed using MDX, some of the syntax are treated slightly differently. For the most accurate parsing and better editor support, we recommend using the `.mdx` extension for files containing MDX syntax. Let's rename the previous file to `greeting.mdx`.
**Note 2:** Since all doc files are parsed using MDX, any HTML is treated as JSX. Therefore, if you need to inline-style a component, follow JSX flavor and provide style objects. This behavior is different from Docusaurus 1. See also [Migrating from v1 to v2](migrating-from-v1-to-v2.md#convert-style-attributes-to-style-objects-in-mdx).
You can also import your own components defined in other files or third-party components installed via npm! Check out the [MDX docs](https://mdxjs.com/) to see what other fancy stuff you can do with MDX.
You can expand the MDX functionalities, using plugins. An MDX plugin is usually a npm package, so you install them like other npm packages using npm. Docusaurus supports both [Remark](https://github.com/remarkjs/remark) and [Rehype](https://github.com/rehypejs/rehype) plugins that work with MDX.
First, install your [Remark](https://github.com/remarkjs/remark/blob/master/doc/plugins.md#list-of-plugins) and [Rehype](https://github.com/rehypejs/rehype/blob/master/doc/plugins.md#list-of-plugins) plugins.
You may want choices of the same kind of tabs to sync with each other. For example, you might want to provide different instructions for users on Windows vs users on macOS, and you want to changing all OS-specific instructions tabs in one click. To achieve that, you can give all related tabs the same `groupId` prop. Note that doing this will persist the choice in `localStorage` and all `<Tab>` instances with the same `groupId` will update automatically when the value of one of them is changed. Not that `groupID` are globally-namespaced.
In addition to the basic Markdown syntax, we use [remark-admonitions](https://github.com/elviswolcott/remark-admonitions) alongside MDX to add support for admonitions. Admonitions are wrapped by a set of 3 colons.
Code blocks are text blocks wrapped around by strings of 3 backticks. You may check out [this reference](https://github.com/mdx-js/specification) for specifications of MDX.
```jsx
console.log('Every repo must come with a mascot.');
```
<!-- TODO: We need to allow users to pick syntax highlighting themes (maybe other than swizzling) -->
Use the matching language meta string for your code block, and Docusaurus will pick up syntax highlighting automatically, powered by [Prism React Renderer](https://github.com/FormidableLabs/prism-react-renderer).
By default, the Prism [syntax highlighting theme](https://github.com/FormidableLabs/prism-react-renderer#theming) we use is [Palenight](https://github.com/FormidableLabs/prism-react-renderer/blob/master/src/themes/palenight.js). You can change this to another theme by passing `theme` field in `prism` as `themeConfig` in your docusaurus.config.js.
By default, Docusaurus comes with this subset of [commonly used languages](https://github.com/FormidableLabs/prism-react-renderer/blob/master/src/vendor/prism/includeLangs.js).
To add syntax highlighting for any of the other [Prism supported languages](https://prismjs.com/#supported-languages), define it in an array of additional languages.
To accomplish this, Docusaurus adds the `docusaurus-highlight-code-line` class to the highlighted lines. You will need to define your own styling for this CSS, possibly in your `src/css/custom.css` with a custom background color which is dependent on your selected syntax highlighting theme. The color given below works for the default highlighting theme (Palenight), so if you are using another theme, you will have to tweak the color accordingly.
To highlight multiple lines, separate the line numbers by commas or use the range syntax to select a chunk of lines. This feature uses the `parse-number-range` library and you can find [more syntax](https://www.npmjs.com/package/parse-numeric-range) on their project details.
With MDX, you can easily create interactive components within your documentation, for example, to display code in multiple programming languages and switching between them using a tabs component.
Instead of implementing a dedicated component for multi-language support code blocks, we've implemented a generic Tabs component in the classic theme so that you can use it for other non-code scenarios as well.
The following example is how you can have multi-language code tabs in your docs. Note that the empty lines above and below each language block is **intentional**. This is a current limitation of MDX, you have to leave empty lines around Markdown syntax for the MDX parser to know that it's Markdown syntax and not JSX.
import Tabs from '@theme/Tabs';
import TabItem from '@theme/TabItem';
<Tabs
defaultValue="js"
values={[
{ label: 'JavaScript', value: 'js', },
{ label: 'Python', value: 'py', },
{ label: 'Java', value: 'java', },
]
}>
<TabItem value="js">
```js
function helloWorld() {
console.log('Hello, world!');
}
```
</TabItem>
<TabItem value="py">
```py
def hello_world():
print 'Hello, world!'
```
</TabItem>
<TabItem value="java">
```java
class HelloWorld {
public static void main(String args[]) {
System.out.println("Hello, World");
}
}
```
</TabItem>
</Tabs>
And you will get the following:
<Tabs
defaultValue="js"
values={[
{ label: 'JavaScript', value: 'js', },
{ label: 'Python', value: 'py', },
{ label: 'Java', value: 'java', },
]
}>
<TabItem value="js">
```js
function helloWorld() {
console.log('Hello, world!');
}
```
</TabItem>
<TabItem value="py">
```py
def hello_world():
print 'Hello, world!'
```
</TabItem>
<TabItem value="java">
```java
class HelloWorld {
public static void main(String args[]) {
System.out.println("Hello, World");
}
}
```
</TabItem>
</Tabs>
You may want to implement your own `<MultiLanguageCode />` abstraction if you find the above approach too verbose. We might just implement one in future for convenience.
If you have multiple of these multi-language code tabs, and you want to sync the selection across the tab instances, refer to the [Syncing tab choices section](#syncing-tab-choices).
