svelte-markdown/README.md

A markdown renderer for Svelte

# Svelte Markdown

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A markdown parser that renders into Svelte Components. Inspired by [ReactMarkdown](https://github.com/remarkjs/react-markdown).

## Installation

You can install it with

```console
$ npm i -S svelte-markdown
```

If you use npm or if you prefer yarn

```console
$ yarn add svelte-markdown
```

If you're using Sapper you might need to install it as a dev dependency.

## Usage

```html
<script>
  import SvelteMarkdown from 'svelte-markdown'
  const source = `
  # This is a header

This is a paragraph.

* This is a list
* With two items
  1. And a sublist
  2. That is ordered
    * With another
    * Sublist inside

| And this is | A table |
|-------------|---------|
| With two    | columns |`
</script>

<SvelteMarkdown {source} />
```

This would render something like

```html
<h1>This is a header</h1>
<p>This is a paragraph.</p>
<ul>
  <li>This is a list</li>
  <li>
    With two items
    <ol start="1">
      <li>And a sublist</li>
      <li>
        That is ordered
        <ul>
          <li>With another</li>
          <li>Sublist inside</li>
        </ul>
      </li>
    </ol>
  </li>
</ul>
<table>
  <thead>
    <tr>
      <th>And this is</th>
      <th>A table</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>With two</td>
      <td>columns</td>
    </tr>
  </tbody>
</table>
```

## Note

Just like with React Markdown, this package doesn't use `{@html ...}` unless you need to render HTML.

## Options

The SvelteMarkdown component accepts the following options:

- `source` - _string_ or _array_ The Markdown source to be parsed, or an array of tokens to be rendered directly.
- `renderers` - _object (optional)_ An object where the keys represent a node type and the value is a Svelte component. This object will be merged with the default renderers. For now you can check how the default renderers are written in the source code at `src/renderers`.
- `options` - _object (optional)_ An object containing [options for Marked](https://marked.js.org/using_advanced#options)

## Rendering From Tokens

For greater flexibility, an array of tokens may be given as `source`, in which case parsing is skipped and the tokens will be rendered directly. This alows you to generate and transform the tokens freely beforehand. Example:

```html
<script>
  import SvelteMarkdown from 'svelte-markdown'
  import { marked } from 'marked'

  const tokens = marked.lexer('this is an **example**')

  marked.walkTokens(tokens, token=> {
    if (token.type == 'strong') token.type = 'em'
    token.raw = token.raw.toUpperCase()
  })
</script>

<SvelteMarkdown source={tokens} />
```

This will render the following:

```html
<p>THIS IS AN <em>EXAMPLE</em></p>
```

## Events

A `parsed` event will be fired when the final tokens have been calculated, allowing you to access the raw token array if needed for things like generating Table of Contents from headings.

```html
<script>
  import SvelteMarkdown from 'svelte-markdown'

  const source = `# This is a header`

  function handleParsed(event) {
    //access tokens via event.detail.tokens
    console.log(event.detail.tokens);
  }
</script>

<SvelteMarkdown {source} on:parsed={handleParsed}>
```

## Available renderers

These would be the property names expected by the `renderers` option.

- `text` - Text rendered inside of other elements, such as paragraphs
- `paragraph` - Paragraph (`<p>`)
- `em` - Emphasis (`<em>`)
- `strong` - Strong/bold (`<strong>`)
- `hr` - Horizontal rule / thematic break (`<hr>`)
- `blockquote` - Block quote (`<blockquote>`)
- `del` - Deleted/strike-through (`<del>`)
- `link` - Link (`<a>`)
- `image` - Image (`<img>`)
- `table` - Table (`<table>`)
- `tablehead` - Table head (`<thead>`)
- `tablebody` - Table body (`<tbody>`)
- `tablerow` - Table row (`<tr>`)
- `tablecell` - Table cell (`<td>`/`<th>`)
- `list` - List (`<ul>`/`<ol>`)
- `listitem` - List item (`<li>`)
- `heading` - Heading (`<h1>`-`<h6>`)
- `codespan` - Inline code (`<code>`)
- `code` - Block of code (`<pre><code>`)
- `html` - HTML node

### Optional List Renderers

For fine detail styling of lists, it can be useful to differentiate between ordered and un-ordered lists.
If either key is missing, the default `listitem` will be used. There are two
optional keys in the `renderers` option which can provide this:

- `orderedlistitem` - A list item appearing inside an ordered list
- `unorderedlistitem` A list item appearing inside an un-ordered list

As an example, if we have an `orderedlistitem`:

```html
<style>
  li::marker {
    color: blue;
  }
</style>

<li><slot></slot></li>
```

Then numbers at the start of ordered list items would be colored blue. Bullets at the start of unordered list items
would remain the default text color.

### Inline Markdown

To use [inline markdown](https://marked.js.org/using_advanced#inline), you can assign the prop `isInline` to the component.

```html
<SvelteMarkdown {source} isInline />
```

## HTML rendering

While the most common flavours of markdown let you use HTML in markdown paragraphs, due to how Svelte handles plain HTML it is currently not possible to do this with this package. A paragraph must be either _all_ HTML or _all_ markdown.

```markdown
This is a **markdown** paragraph.

<p>This is an <strong>HTML</strong> paragraph</p>
```

Note that the HTML paragraph must be enclosed within `<p>` tags.

## Developing

Some tests have been added to the `tests` folder. You can clone this repo and create another svelte app and link it to this repo to try modifying it.

You can clone this repo and do the following:

```console
$ yarn
$ yarn link
$ yarn dev
```

This will watch all changes and make the project linkable. Now on the app you created you can link it with:

```console
$ yarn link svelte-markdown
```

And then import it like in the example above.

As of now the only external dependency of this project is `marked`.

## Related

- [ReactMarkdown](https://github.com/remarkjs/react-markdown) - React library to render markdown using React components. Inspiration for this library.
- [Svelte](https://svelte.dev) - JavaScript front-end framework.
- [Marked](https://marked.js.org/) - Markdown parser