fairyfly
v0.2.0-beta
    Serverless-first. Built for cold starts, tight memory, and one binary.Deploy guide →

    Examples

    Copy any block into a file, run it with ff, check the output. Each entry names its source guide for the full walkthrough.

    Hello, world

    // hello.js
console.log("hello from fairyfly");
    ff hello.js
# hello from fairyfly

    Guide: Quickstart.

    HTTP server

    // server.js
http.serve({ port: 3000 }, (url, method, body) => {
  if (url === "/") return new Response("hello");
  return new Response("not found", { status: 404 });
});
    ff server.js
curl http://127.0.0.1:3000/
# hello

    Routing, JSON REST API, SQLite-backed notes API: HTTP Server guide. Method/options tables: http API.

    Fetch client

    // client.js
const res = await fetch("https://example.com/");
console.log(res.status, res.ok);
console.log((await res.text()).length);
    ff client.js

    POST JSON, redirect rules, private-CA trust, mirror script: Fetch Client guide. Types and readers: fetch API.

    WebSocket chat room

    // room.js
const peers = new Set();
http.serve(
  {
    port: 3000,
    websocket: {
      open: (socket) => peers.add(socket),
      message: (socket, data) => {
        for (const peer of peers) peer.send(data);
      },
      close: (socket) => peers.delete(socket),
    },
  },
  (url, method, body) => new Response(`online: ${peers.size}`),
);
    ff room.js

    Upgrades are automatic when the websocket block is present — no handler branch. Presence counter, binary frames, client API: WebSocket guide.

    TLS + WSS

    openssl req -x509 -newkey rsa:2048 -nodes -days 365 \
  -keyout key.pem -out cert.pem -subj "/CN=localhost" \
  -addext "subjectAltName=DNS:localhost,IP:127.0.0.1"
ff start --cert cert.pem --key key.pem
curl -k https://127.0.0.1:3000/

    Dev certs, self-trust cases, WSS echo: TLS guide. ALPN negotiation: HTTP/2 guide.

    SQLite notes API

    // notes.js
const db = Database.open("notes.db");
db.execNoArgs("CREATE TABLE IF NOT EXISTS notes (id INTEGER PRIMARY KEY, text TEXT)");
db.exec("INSERT INTO notes (text) VALUES (?)", ["buy milk"]);
console.log(db.rows("SELECT * FROM notes"));
db.close();
// [ { id: 1, text: "buy milk" } ]

    Transactions, lastInsertRowId(), busy timeout: SQLite API.

    Workers (hash offload)

    // main.js
const w = new Worker("./hasher.js", { data: { rounds: 50000 } });
w.onmessage = (e) => console.log("hash:", e.data);
w.postMessage({ password: "hunter2" });
    // hasher.js
const cfg = globalThis.workerData;
onmessage = (e) => {
  let acc = e.data.password;
  for (let i = 0; i < cfg.rounds; i++) acc = acc.split("").reverse().join("");
  postMessage({ hex: acc.slice(0, 32), rounds: cfg.rounds });
};

    Spawn rules, { data } vs workerData, terminate, pool pattern: Workers guide.

    Packages (markdown blog)

    ff init -y blog && cd blog
ff imprint marked@18.0.11
    import { marked } from "marked";
http.serve({ port: 3000 }, () => new Response(marked.parse("# Hello"), {
  headers: { "content-type": "text/html" },
}));

    Install/remove/rebuild/CI: Packages guide. Resolution rules: Modules guide.

    Testing a JSON endpoint

    // test/notes.test.js
import { check, done } from "./lib.mjs";

http.serve({ port: 3902 }, (url, method, body) => {
  if (url === "/notes" && method === "POST") {
    const data = JSON.parse(body || "{}");
    if (!data.text) return Response.json({ error: "text is required" }, { status: 400 });
    return Response.json({ id: 1, text: data.text }, { status: 201 });
  }
  return new Response("not found", { status: 404 });
});

const ok = await fetch("http://127.0.0.1:3902/notes", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({ text: "buy milk" }),
});
check("creates", ok.status === 201);
done("notes");
    ff test notes
# OK   test/notes.test.js

    check/done, server fixtures, run.sh: Testing guide.

    Bytecode ship

    ff compile app.js -o app.ffbc
# ✓ Compiled app.js → app.ffbc (12345 bytes)
ff app.ffbc

    When to compile, caps, stripped traces: Bytecode guide.

    Timers + process CLI

    // poll.js
let delay = 100;
function poll() {
  fetch("https://api.example.com/health")
    .then((r) => { console.log("up:", r.ok); delay = 100; })
    .catch(() => { delay = Math.min(delay * 2, 5000); })
    .finally(() => setTimeout(poll, delay).unref());
}
poll();
    // tool.js
const [cmd, ...rest] = process.argv.slice(2);
if (cmd === "greet") console.log(`hello, ${rest[0] ?? "world"}`);
else { console.error("usage: tool.js <greet [name]>"); process.exit(1); }

    Sleep, intervals, unref, microtasks: Timers guide. argv/env/exit: Process guide. Env vars: Env guide.

    Blobs and forms

    const form = new FormData();
form.append("name", "ada");
form.append("avatar", new Blob(["<bytes>"], { type: "image/png" }), "avatar.png");
await fetch("https://api.example.com/submit", { method: "POST", body: form });

    slice, round-tripping, file-drop endpoint: Blob and FormData.

    Deploy checklist

    ./scripts/fetch-vendors.sh && make build && make install
FF_ECHO=1 ff start & curl -i http://127.0.0.1:3000/health; kill %1
ff start

    Docker, ff start, production TLS, health endpoint: Deploy guide. Install paths: Installation. Caps: Limitations.