Teaching Parametric Design Backend

An Express + TypeScript API that forwards code-generation prompts to the OpenRouter API, enforces a JavaScript-only context, and returns HTML-highlighted snippets with quick reference links.

Setup

1. Copy .env.example to .env and provide your OpenRouter credentials.
2. Install dependencies (requires Node.js 18+ for the built-in fetch API):

npm install

Scripts

• npm run dev — start the API in watch mode via ts-node.
• npm run build — compile TypeScript to dist/.
• npm start — run the compiled server from dist/.
• npm test — run the Vitest suite (uses JSDOM for HTML validation).

API

POST /api/generate

Request body:

{
  "question": "How do I animate a div on click?"
}

Behavior:

• Wraps the question with a system prompt that demands only JavaScript code (no Markdown).
• Sends the request to OpenRouter using the configured model.
• Highlights the returned JavaScript with highlight.js and converts selected function names into links to MDN.

Response body:

{
  "html": "<pre><code class=\"hljs language-javascript\">…</code></pre>"
}

Environment Variables

• PORT — API port (default: 3000).
• OPENROUTER_API_KEY — required OpenRouter token.
• OPENROUTER_MODEL — model slug (default: openai/gpt-4o-mini).
• OPENROUTER_SITE_URL — value forwarded to OpenRouter HTTP-Referer header.
• OPENROUTER_APP_TITLE — value forwarded to OpenRouter X-Title header.

Notes

• The service expects the OpenRouter API key to be present at runtime. Without it, requests will fail.
• Function references such as fetch, console.log, document.querySelector, and addEventListener are automatically linked to MDN in the generated HTML.