markdown_yo — WebAssembly API

A high-performance Markdown-to-HTML converter compiled to WebAssembly.

Installation

npm install markdown_yo

Quick Start

import { createRenderer } from "markdown_yo";

const md = await createRenderer();
const html = md.render("# Hello\n\n**World**");
console.log(html);
// <h1>Hello</h1>
// <p><strong>World</strong></p>

API

createRenderer(wasmOptions?): Promise<MarkdownRenderer>

Creates a new renderer instance by loading the WebAssembly module. Call this once and reuse the returned renderer for all conversions.

Parameters:

| Name | Type | Description | |------|------|-------------| | wasmOptions | WasmOptions | Optional. Configuration for the Emscripten module loader. |

WasmOptions:

| Property | Type | Description | |----------|------|-------------| | locateFile | (path: string, prefix: string) => string | Custom resolver for the .wasm file location |

Returns: Promise<MarkdownRenderer>

MarkdownRenderer.render(markdown, options?): string

Render a Markdown string to HTML.

Parameters:

| Name | Type | Description | |------|------|-------------| | markdown | string | The Markdown source text | | options | RenderOptions | Optional. Rendering options |

RenderOptions:

| Option | Type | Default | Description | |--------|------|---------|-------------| | commonmark | boolean | false | Use CommonMark-compliant parsing | | html | boolean | false | Allow raw HTML tags in output | | typographer | boolean | false | Enable typographic replacements (" → ", -- → —, etc.) | | subscript | boolean | false | Enable ~subscript~ syntax → <sub> | | superscript | boolean | false | Enable ^superscript^ syntax → <sup> | | mark | boolean | false | Enable ==highlight== syntax → <mark> | | math | boolean | false | Enable $inline$ and $$block$$ math syntax | | fullFeatures | boolean | false | Enable all optional features at once |

Returns: string — the rendered HTML

MarkdownRenderer.destroy(): void

Release WASM module resources. The renderer should not be used after calling this.

Examples

Node.js

const { createRenderer } = require("markdown_yo");

async function main() {
  const md = await createRenderer();

  // Basic rendering
  console.log(md.render("# Title\n\nA paragraph with **bold** text."));

  // With CommonMark mode
  console.log(md.render(source, { commonmark: true }));

  // Allow HTML passthrough
  console.log(md.render("<div>raw html</div>", { html: true }));

  md.destroy();
}

main();

Browser (bundler)

import { createRenderer } from "markdown_yo";

const md = await createRenderer();
document.getElementById("preview").innerHTML = md.render(markdownSource);

Browser (script tag)

<script src="https://unpkg.com/markdown_yo/markdown_yo_wasm_api.js"></script>
<script src="https://unpkg.com/markdown_yo/index.js"></script>
<script>
  markdownYo.createRenderer().then((md) => {
    const html = md.render("# Hello from **markdown_yo**!");
    document.body.innerHTML = html;
  });
</script>

Custom WASM file location

If you host the .wasm file separately (e.g., on a CDN), use locateFile:

const md = await createRenderer({
  locateFile: (path) => `https://cdn.example.com/wasm/${path}`,
});

TypeScript

import { createRenderer, type RenderOptions } from "markdown_yo";

const md = await createRenderer();

const opts: RenderOptions = { commonmark: true, html: true };
const html: string = md.render("# Hello", opts);

Supported Markdown Features

• CommonMark — 815/826 spec tests pass (98.7%)
• GFM Tables — pipe tables with alignment
• Strikethrough — ~~text~~
• Fenced code blocks — with language info strings
• HTML passthrough — when html: true is set
• Typographic replacements — when typographer: true is set
• Subscript — ~text~ → <sub>text</sub> (when subscript: true)
• Superscript — ^text^ → <sup>text</sup> (when superscript: true)
• Mark/Highlight — ==text== → <mark>text</mark> (when mark: true)
• Math — $inline$ and $$block$$ math (when math: true)

Live Demo

Try it in the browser: https://shd101wyy.github.io/markdown_yo/

Building from Source

Requires the Yo compiler and Emscripten.

# Install Yo compiler
npm install -g @shd101wyy/yo

# Build the WASM API target
yo build wasm_api

# Output files:
#   yo-out/wasm32-emscripten/bin/markdown_yo_wasm_api.js
#   yo-out/wasm32-emscripten/bin/markdown_yo_wasm_api.wasm