Slowdown

A focused HTML-to-Markdown converter with critical bug fixes.

What is Slowdown?

Slowdown is a streamlined fork of Showdown, specialized exclusively for HTML → Markdown conversion.

The original Showdown library is no longer actively maintained and contains several critical bugs in its HTML-to-Markdown functionality. Slowdown fixes these issues and removes all Markdown→HTML code to focus solely on HTML→Markdown conversion.

Why Slowdown?

Fixed Bugs

1. Tables without <thead> are converted properly

   • Original bug: Tables missing thead elements would fail or produce incorrect output
   • Fixed: Column count is now correctly determined from table structure

2. HTML content in <pre> tags no longer crashes

   • Original bug: .toLowerCase() called on text nodes caused crashes
   • Fixed: Uses firstElementChild instead of firstChild to avoid text node errors

3. Consecutive <pre> tags are preserved

   • Original bug: Whitespace cleaning removed structural nodes between consecutive pre tags
   • Fixed: Clean operation runs before pre tag substitution

Installation

npm

npm install slowdown

From GitHub

npm install github:i-a-n/slowdown

Local Development

git clone [email protected]:i-a-n/slowdown.git
cd slowdown
npm install
npm test

Usage

Node.js

const slowdown = require('slowdown');
const converter = new slowdown.Converter();

const html = '<h1>Hello World</h1><p>This is <strong>HTML</strong>.</p>';
const markdown = converter.makeMarkdown(html);

console.log(markdown);
// # Hello World
//
// This is **HTML**.

Tables

const html = `
<table>
  <tbody>
    <tr><td>Name</td><td>Age</td></tr>
    <tr><td>Alice</td><td>30</td></tr>
    <tr><td>Bob</td><td>25</td></tr>
  </tbody>
</table>
`;

const markdown = converter.makeMarkdown(html);
// | Name  | Age |
// | ----- | --- |
// | Alice | 30  |
// | Bob   | 25  |

Pre-formatted Code

const html = '<pre>function hello() {\n  console.log("world");\n}</pre>';
const markdown = converter.makeMarkdown(html);

API

new slowdown.Converter([options])

Creates a new converter instance.

Parameters:

• options (Object, optional): Converter options (inherited from Showdown, most MD→HTML options removed)

Returns: Converter instance

converter.makeMarkdown(html)

Converts an HTML string to Markdown.

Parameters:

• html (String): HTML string to convert

Returns: Markdown string

Building

Slowdown uses Grunt for building distribution files:

# Install dependencies
npm install

# Build distribution files
npx grunt build-without-test

# Run tests
npm test

Note: We plan to modernize the build system in a future release (replace Grunt with esbuild or similar).

Testing

# Run all tests
npm test

# Run only functional tests
npx grunt test-functional

# Run only unit tests
npx grunt test-unit

What's Removed from Showdown?

• ❌ Markdown → HTML conversion (makeHtml() method)
• ❌ All MD→HTML subparsers (~30 files)
• ❌ Extensive documentation for unused features
• ❌ Browser-based testing (Karma)
• ❌ mkdocs documentation system
• ❌ Bower support
• ❌ GitHub workflow configurations

Project Status

Slowdown is actively maintained for HTML→Markdown conversion. This is a focused tool, not a general-purpose Markdown library.

Version: 2.0.0 (major rewrite)

License

MIT License - maintained from the original Showdown project.

Copyright (c) 2018-2021 ShowdownJS
Copyright (c) 2026 Slowdown (fork)

See LICENSE for full details.

Credits

Slowdown is a fork of Showdown by Estevão Santos, which itself was based on the original Markdown converter by John Gruber.

Contributing

This is a focused fork with a specific purpose. Major feature additions are generally not accepted, but bug fixes and performance improvements are welcome.

To report bugs:

1. Check if it's reproducible with the latest version
2. Create a minimal test case
3. Open an issue on GitHub with reproduction steps

Links

• GitHub: https://github.com/i-a-n/slowdown
• npm: (package not yet published)
• Original Showdown: https://github.com/showdownjs/showdown