Melina.js

A lightweight, streaming-first web framework for Bun that delivers blazing fast user experiences with zero configuration.

Features

• Simplified Setup - Define a server handler and start building.
• Streaming by Default - Return AsyncGenerators from your handler for immediate Time to First Contentful Paint.
• Dynamic Import Maps - Generate modern ES module import maps from your package.json on the fly.
• On-Demand Asset Building - Client-side JavaScript and CSS are built when requested during development, and cached in production.
• Framework Agnostic - Works with React, Vue, Svelte, or vanilla JS on the client-side.
• Built-in Performance Measurement - Debug and optimize with ease using the measure utility.
• Tailwind CSS JIT - Seamless Tailwind CSS integration for your assets.
• 🔥 NEW: MCP Server - MCP (Model Context Protocol)

Installation

bun add melinajs

Quick Start

MCP Example

Web Example (Vanilla JS)

Web Example (React with Tailwind CSS)

How It Works (Web)

Melina.js simplifies web application delivery with a handler-centric approach:

1. Request Handling: When a request comes in, it's routed to the main handler function you provide to serve().
2. Server-Side Logic: Your handler processes the request. You can implement routing, API endpoints, or page generation logic.
3. Streaming HTML: For HTML pages, your handler can return an AsyncGenerator<string>. Melina immediately starts streaming the first chunk of HTML to the browser. This allows the browser to start parsing and rendering content without waiting for all server-side processing to complete.
4. Asset Serving:
   • You use the asset(filePath) function within your server-side rendering logic (e.g., inside your streaming generator) to get a URL for a client-side JavaScript or CSS file.
   • Development: When a request for an asset URL comes, Melina (via Bun) builds that specific asset on-the-fly (e.g., transpiling TSX, processing CSS with Tailwind).
   • Production: Assets are built once and served with long-cache headers (hashed filenames ensure cache-busting).
5. Import Map Injection: You can use the imports([...dependencies]) function to generate an import map from your project's package.json. This import map is then manually injected into your HTML stream, allowing you to use bare module specifiers for your client-side ES modules (e.g., import React from 'react').
6. Data Injection: Server-side data can be injected into the HTML stream by embedding a <script> tag that assigns data to a global variable (e.g., window.SERVER_DATA). The client-side code can then pick this up.

This approach significantly improves perceived performance by prioritizing Time to First Contentful Paint (TTFCP) and enabling progressive rendering.

API

import { serve, asset, imports } from "melinajs/web";

• serve(handler: (req: Request) => Response | AsyncGenerator<string> | Promise<...>): Starts the Bun server with your main request handler. The handler receives the standard Request object and can return:

  • A Response object (e.g., Response.json(...), new Response(...)).
  • An AsyncGenerator<string> for streaming HTML content.
  • A string (will be returned as text/html).
  • A plain object (will be returned as application/json).
  • A Promise that resolves to any of the above.

• asset(filePath: string): Promise<string>: Takes a path to a client-side asset (e.g., ./App.client.tsx, ./styles.css). Returns a Promise<string> that resolves to a fingerprinted URL path (e.g., /App.client-X1Y2Z3.js) for that asset. In development, the asset is built on first request. In production, it's built once. Supports TypeScript/TSX, JavaScript, and CSS (with Tailwind JIT via bun-plugin-tailwind if App.css uses @import "tailwindcss").

• imports(subpaths?: string[], pkgJson?: any, lockFile?: any): Promise<ImportMap>: Generates an import map object.

  • subpaths (optional): An array of module subpaths to include (e.g., ['react-dom/client']). Base packages from dependencies in package.json are included by default.
  • pkgJson (optional): Pass a pre-loaded package.json object. Defaults to loading ./package.json.
  • lockFile (optional): Pass a pre-loaded bun.lockb (parsed as JSON) object. Defaults to loading ./bun.lockb. It uses esm.sh as the CDN for ES modules and correctly resolves versions and peer dependencies based on your package.json and bun.lockb.

API Routes

// server.ts
serve(async (req: Request) => {
  const url = new URL(req.url);

  if (url.pathname === '/api/users' && req.method === 'GET') {
    // Handle GET /api/users
    const users = [{ id: 1, name: "Ada" }, { id: 2, name: "Grace" }];
    return Response.json({ users });
  }

  if (url.pathname.startsWith('/api/users/') && req.method === 'POST') {
    // Handle POST /api/users/:id
    const body = await req.json();
    return Response.json({ message: "User created/updated", data: body }, { status: 201 });
  }

  // ... your HTML page routes
  if (url.pathname === '/') {
    // return streamMyPage();
  }

  return new Response("Not Found", { status: 404 });
});

Import Maps Generation

Melina uses Import Maps to manage client-side dependencies using modern ES modules without complex bundling for third-party libraries.

The imports() function, obtained from useServer(), automates this:

import { useServer } from "melinajs";
// import packageJson from "./package.json"; // Optional: if you want to pass it explicitly

const { imports } = useServer();

// Example: Generate import map including react, react-dom/client, and others from package.json
const importMapObject = await imports(
  ['react', 'react-dom/client'] // Specify exact subpaths if needed
  // packageJson // Optionally pass your package.json object
);

// importMapObject will look like:
// {
//   "imports": {
//     "react": "https://esm.sh/[email protected]?dev",
//     "react-dom/client": "https://esm.sh/[email protected]/client?dev",
//     // ... other dependencies from your package.json
//   }
// }

// Then, in your HTML streaming function:
// yield `<script type="importmap">${JSON.stringify(importMapObject, null, 2)}</script>`;

This automatically:

• Extracts versions from your package.json (and bun.lockb for transitive/peer dependency resolution).
• Configures CDN URLs (using esm.sh by default).
• Handles peer dependencies correctly.
• Appends ?dev to CDN URLs in development for better debugging.

FAQs

Is Melina production-ready?

Yes! When NODE_ENV is set to production (e.g., NODE_ENV=production bun run server.ts):

• Assets built by asset() are cached with fingerprinted names for long-term browser caching.
• JavaScript and CSS are minified.
• Source maps are disabled for assets.
• The ?dev parameter is removed from esm.sh URLs in import maps.

How does Melina compare to Next.js or Remix?

Melina is significantly more lightweight and takes a different philosophical approach:

• Minimal Build Step: No complex global build step for your application. Assets are built on-demand by Bun.
• HTML Generation is Explicit: You construct HTML, often via streaming, directly in your server-side TypeScript/JavaScript. There are no special file-system routing conventions for pages beyond what you implement in your handler.
• Handler-Centric: All server logic (routing, API, page serving) typically resides in or is dispatched from the main handler function provided to serve().
• Streaming-First by Design: AsyncGenerators are a natural way to stream HTML.
• Leverages Bun's Strengths: Built specifically for the Bun runtime, utilizing its speed, built-in TypeScript/JSX support, and asset building capabilities.
• Closer to the Platform: Uses standard Web APIs like Request, Response, and leverages Import Maps for client-side modules.

Next.js and Remix are more feature-rich, opinionated frameworks with their own routing conventions, data-loading patterns, and extensive build systems. Melina offers a leaner, more direct way to build fast, streaming web applications on Bun.

Can I use Melina with TypeScript?

Yes, Melina is built with TypeScript in mind and works seamlessly with it. Bun handles TypeScript transpilation automatically for your server code and any assets processed by asset().

Contributing

Contributions are welcome! Please feel free to submit a Pull Request or open an issue.

License

MIT