markdown

The markdown module provides bidirectional conversion between Markdown and HTML. It supports common Markdown syntax including headings, emphasis, code blocks, lists, links, images, and GitHub Flavored Markdown (GFM) extensions like tables, task lists, and autolinks.

import "markdown" for Markdown

Markdown Class

Markdown

Markdown to HTML converter

Static Methods

Markdown.toHtml(text) → String

Converts Markdown text to HTML.

text (String) - Markdown text
Returns: HTML string

var html = Markdown.toHtml("# Hello World")
System.print(html)  // <h1>Hello World</h1>

Markdown.toHtml(text, options) → String

Converts Markdown text to HTML with options.

text (String) - Markdown text
options (Map) - Conversion options
Returns: HTML string

Markdown.fromHtml(html) → String

Converts HTML to Markdown text.

html (String) - HTML string
Returns: Markdown text

var md = Markdown.fromHtml("<h1>Hello World</h1>")
System.print(md)  // # Hello World

Markdown.fromHtml(html, options) → String

Converts HTML to Markdown text with options.

html (String) - HTML string
options (Map) - Conversion options
Returns: Markdown text

Options

toHtml Options

Option	Type	Default	Description
`safeMode`	Bool	`false`	Escape HTML in input to prevent XSS

fromHtml Options

Option	Type	Default	Description
`stripUnknown`	Bool	`true`	Strip unknown HTML tags, keeping their content

Supported Syntax

Headings

# Heading 1
## Heading 2
### Heading 3
#### Heading 4
##### Heading 5
###### Heading 6

Converts to <h1> through <h6> tags.

Emphasis

*italic* or _italic_
**bold** or __bold__
~~strikethrough~~

Converts to <em>, <strong>, and <del> tags.

Code

Inline `code` here

```
Code block
Multiple lines
```

```javascript
const x = 1;
```

Inline code uses <code>, blocks use <pre><code>. Language identifiers after the opening fence add a class="language-{lang}" attribute to the code element for syntax highlighting integration.

Lists

Unordered:
- Item 1
- Item 2
* Also works
+ And this

Ordered:
1. First
2. Second
3. Third

Creates <ul> and <ol> with <li> items.

Task Lists (GFM)

- [ ] Unchecked task
- [x] Checked task
- [X] Also checked

Creates <ul class="task-list"> with checkbox inputs. Checkboxes are rendered as disabled to indicate they are display-only.

Tables (GFM)

| Header 1 | Header 2 | Header 3 |
|----------|:--------:|---------:|
| Left     | Center   | Right    |
| Cell     | Cell     | Cell     |

Creates HTML tables with <thead> and <tbody>. Column alignment is specified in the separator row using colons: :--- for left, :---: for center, ---: for right.

Autolinks (GFM)

Visit https://example.com for more info.
Email me at user@example.com

Bare URLs starting with http:// or https:// and email addresses are automatically converted to clickable links.

Links and Images

[Link text](https://example.com)
![Alt text](image.png)

Creates <a href="..."> and <img src="..." alt="...">.

Blockquotes

> This is a quote
> Multiple lines

Creates <blockquote> with <p> content.

Horizontal Rule

---
***
___

Creates <hr> tag.

Paragraphs

Text separated by blank lines becomes <p> elements.

HTML to Markdown Conversions

The fromHtml method converts the following HTML elements to Markdown:

HTML	Markdown
`<h1>` to `<h6>`	`#` to `######`
`<strong>`, `<b>`	`text`
`<em>`, `<i>`	`text`
`<code>`	`text`
`<pre><code>`	Fenced code block
`<a href="url">`	`[text](url)`
`<img src="url" alt="">`	`![alt](url)`
`<ul><li>`	`- item`
`<ol><li>`	`1. item`
`<blockquote>`	`> text`
`<hr>`	`---`
`<del>`, `<s>`	`~~text~~`
`<table>`	GFM table syntax

Container tags (<div>, <span>, <section>, etc.) are stripped but their content is preserved. Script and style tags are removed entirely.

Examples

Basic Conversion

import "markdown" for Markdown

var md = "
# Welcome

This is a **Markdown** document with:

- Lists
- *Emphasis*
- `Code`

Visit [Wren](https://wren.io) for more.
"

var html = Markdown.toHtml(md)
System.print(html)

Safe Mode for User Content

import "markdown" for Markdown

var userInput = "# Title\n<script>alert('xss')</script>\nContent here."

var safeHtml = Markdown.toHtml(userInput, {"safeMode": true})
System.print(safeHtml)

Rendering a Blog Post

import "markdown" for Markdown
import "io" for File

var postContent = File.read("post.md")
var html = Markdown.toHtml(postContent)

var page = "<html>
<head><title>Blog</title></head>
<body>
<article>
%(html)
</article>
</body>
</html>"

File.write("post.html", page)

Code Blocks with Language Classes

import "markdown" for Markdown

var md = "
```wren
System.print(\"Hello, World!\")
```
"

var html = Markdown.toHtml(md)
System.print(html)
// <pre><code class="language-wren">System.print("Hello, World!")</code></pre>

Tables

import "markdown" for Markdown

var md = "
| Name  | Age | City      |
|-------|----:|:----------|
| Alice |  30 | New York  |
| Bob   |  25 | London    |
"

var html = Markdown.toHtml(md)
System.print(html)

Task Lists

import "markdown" for Markdown

var md = "
## Project Tasks

- [x] Design database schema
- [x] Implement API endpoints
- [ ] Write unit tests
- [ ] Deploy to production
"

var html = Markdown.toHtml(md)
System.print(html)

Combining with Templates

import "markdown" for Markdown
import "jinja" for Environment, DictLoader

var env = Environment.new(DictLoader.new({
    "base": "<html><body></body></html>"
}))

var md = "# Hello\n\nThis is **Markdown**."
var content = Markdown.toHtml(md)

var html = env.getTemplate("base").render({"content": content})
System.print(html)

Converting HTML to Markdown

import "markdown" for Markdown

var html = "
<html>
<body>
<h1>Article Title</h1>
<p>This is <strong>important</strong> content.</p>
<ul>
<li>First item</li>
<li>Second item</li>
</ul>
</body>
</html>
"

var md = Markdown.fromHtml(html)
System.print(md)
// # Article Title
//
// This is **important** content.
//
// - First item
// - Second item

Cleaning HTML for Plain Text

import "markdown" for Markdown

var webContent = "<div><script>alert('xss')</script><p>Safe <b>content</b></p></div>"
var clean = Markdown.fromHtml(webContent)
System.print(clean)  // Safe **content**

Warning

When rendering user-provided Markdown, always use safeMode: true to prevent cross-site scripting (XSS) attacks. Safe mode escapes HTML entities in the input text.

Note

Language identifiers after code fences (e.g., ```wren) are added as class="language-{lang}" to the code element. This is compatible with syntax highlighters like Prism.js or highlight.js.