bun.sh/examples/bun/http.ts

// Start a fast HTTP server from a function
Bun.serve({
  fetch(req) {
    return new Response("Hello World!");
  },

  // this is called when fetch() throws or rejects
  error(err: Error) {
    return new Response("uh oh! :(" + err.toString(), { status: 500 });
  },

  // this boolean enables the bun's default error handler
  // sometime after the initial release, it will auto reload as well
  development: process.env.NODE_ENV !== "production",
  // note: this isn't node, but for compatibility bun supports process.env + more stuff in process

  // SSL is enabled if these two are set
  // certFile: './cert.pem',
  // keyFile: './key.pem',

  port: 8080, // number or string
  hostname: "localhost", // defaults to 0.0.0.0
});

// Start a fast HTTP server from the main file's export
export default {
  fetch(req) {
    return new Response(
      `This is another way to start a server! 
       if the main file export default's an object 
       with 'fetch'. Bun automatically calls Bun.serve`
    );
  },
  // so autocomplete & type checking works
} as Bun.Serve;