feat(wasm): add Node.js ES module wrapper

- Create async/sync JavaScript API wrapper
- Configure package.json with .mjs build script
- Handle WASM initialization and module loading

Author: jp-knj

wasm/lib/index.mjs

@@ -0,0 +1,80 @@
+import { readFile } from 'node:fs/promises';
+import { fileURLToPath } from 'node:url';
+import { dirname, join } from 'node:path';
+
+// Dynamic import to handle the ES module
+let wasmModule = null;
+
+async function loadWasmModule() {
+  if (!wasmModule) {
+    wasmModule = await import('../pkg/markdown_rs_wasm.mjs');
+  }
+  return wasmModule;
+}
+
+// Initialize WASM module once
+let initialized = false;
+let initPromise = null;
+
+async function ensureInitialized() {
+  if (initialized) return;
+  if (!initPromise) {
+    const wasm = await loadWasmModule();
+    // Read WASM file for Node.js
+    const __dirname = dirname(fileURLToPath(import.meta.url));
+    const wasmPath = join(__dirname, '..', 'pkg', 'markdown_rs_wasm_bg.wasm');
+    const wasmBuffer = await readFile(wasmPath);
+
+    initPromise = wasm.default({ module_or_path: wasmBuffer }).then(() => {
+      initialized = true;
+    });
+  }
+  await initPromise;
+}
+
+/**
+ * Convert markdown to HTML using CommonMark
+ * @param {string} input - Markdown text
+ * @returns {Promise<string>} HTML output
+ */
+export async function toHtml(input) {
+  await ensureInitialized();
+  const wasm = await loadWasmModule();
+  return wasm.to_html(input);
+}
+
+/**
+ * Convert markdown to HTML with options
+ * @param {string} input - Markdown text
+ * @param {Object} options - Parsing options
+ * @param {boolean} [options.gfm] - Enable GitHub Flavored Markdown
+ * @param {boolean} [options.mdx] - Enable MDX
+ * @param {boolean} [options.frontmatter] - Enable frontmatter
+ * @param {boolean} [options.allowDangerousHtml] - Allow raw HTML
+ * @param {boolean} [options.allowDangerousProtocol] - Allow dangerous protocols
+ * @returns {Promise<string>} HTML output
+ */
+export async function toHtmlWithOptions(input, options) {
+  await ensureInitialized();
+  const wasm = await loadWasmModule();
+  return wasm.to_html_with_options(input, options);
+}
+
+// Also export sync versions after initialization
+export function toHtmlSync(input) {
+  if (!initialized || !wasmModule) {
+    throw new Error('WASM not initialized. Call toHtml() first or await init()');
+  }
+  return wasmModule.to_html(input);
+}
+
+export function toHtmlWithOptionsSync(input, options) {
+  if (!initialized || !wasmModule) {
+    throw new Error('WASM not initialized. Call toHtmlWithOptions() first or await init()');
+  }
+  return wasmModule.to_html_with_options(input, options);
+}
+
+export async function init() {
+  await ensureInitialized();
+}

wasm/package.json

@@ -0,0 +1,31 @@
+{
+  "name": "markdown-rs-wasm",
+  "version": "0.0.1",
+  "description": "WebAssembly bindings for markdown-rs",
+  "type": "module",
+  "exports": "./lib/index.mjs",
+  "files": [
+    "lib/",
+    "pkg/",
+    "README.md"
+  ],
+  "scripts": {
+    "build": "wasm-pack build --target web --out-dir pkg && mv pkg/markdown_rs_wasm.js pkg/markdown_rs_wasm.mjs",
+    "test": "node --test test/index.test.mjs",
+    "example:basic": "node examples/basic.mjs",
+    "example:options": "node examples/with-options.mjs"
+  },
+  "keywords": [
+    "markdown",
+    "commonmark",
+    "wasm",
+    "webassembly",
+    "mdx",
+    "gfm"
+  ],
+  "license": "MIT",
+  "repository": "https://github.com/wooorm/markdown-rs",
+  "engines": {
+    "node": ">=16.0.0"
+  }
+}