elysia

bun create elysia my-api
cd my-api
bun run dev

// src/index.ts — Elysia REST API with validation
/**
 * Type-safe REST API using Elysia.
 * Body/query/params are validated at runtime AND typed at compile time.
 * No separate type definitions needed — schema IS the type.
 */
import { Elysia, t } from "elysia";

const app = new Elysia()
  // GET with typed query params
  .get("/users", async ({ query }) => {
    const { page, limit } = query;
    // page and limit are typed as numbers
    return { users: [], page, limit };
  }, {
    query: t.Object({
      page: t.Number({ default: 1 }),
      limit: t.Number({ default: 20, maximum: 100 }),
    }),
  })

  // POST with body validation
  .post("/users", async ({ body }) => {
    // body is typed as { name: string, email: string }
    const user = { id: crypto.randomUUID(), ...body, createdAt: new Date() };
    return user;
  }, {
    body: t.Object({
      name: t.String({ minLength: 2, maxLength: 100 }),
      email: t.String({ format: "email" }),
    }),
  })

  // Path params + response schema
  .get("/users/:id", async ({ params, error }) => {
    const user = await findUser(params.id);
    if (!user) return error(404, { message: "User not found" });
    return user;
  }, {
    params: t.Object({
      id: t.String({ format: "uuid" }),
    }),
  })

  // DELETE with auth guard
  .delete("/users/:id", async ({ params }) => {
    await deleteUser(params.id);
    return { deleted: true };
  }, {
    params: t.Object({ id: t.String() }),
    beforeHandle: ({ headers, error }) => {
      if (headers.authorization !== `Bearer ${process.env.ADMIN_TOKEN}`) {
        return error(401, { message: "Unauthorized" });
      }
    },
  })

  .listen(3000);

console.log(`🦊 Elysia running at ${app.server?.url}`);

// src/ws.ts — Type-safe WebSocket with Elysia
import { Elysia, t } from "elysia";

const app = new Elysia()
  .ws("/chat", {
    body: t.Object({
      type: t.Union([t.Literal("message"), t.Literal("ping")]),
      content: t.Optional(t.String()),
      room: t.String(),
    }),
    open(ws) {
      const room = ws.data.query.room || "general";
      ws.subscribe(room);
      ws.publish(room, JSON.stringify({ type: "system", content: `User joined ${room}` }));
    },
    message(ws, { type, content, room }) {
      if (type === "message" && content) {
        ws.publish(room, JSON.stringify({ type: "message", content, from: ws.id }));
      }
      if (type === "ping") {
        ws.send(JSON.stringify({ type: "pong" }));
      }
    },
    close(ws) {
      ws.unsubscribeAll();
    },
  })
  .listen(3000);

// client.ts — Auto-typed API client generated from Elysia server
/**
 * Eden Treaty creates a fully typed client from your Elysia app type.
 * No codegen, no OpenAPI parsing — just TypeScript inference.
 */
import { treaty } from "@elysiajs/eden";
import type { App } from "./src/index";  // Import the app TYPE

const api = treaty<App>("localhost:3000");

// All methods, params, body, and responses are fully typed
const { data: users } = await api.users.get({ query: { page: 1, limit: 10 } });
//    ^? { users: User[], page: number, limit: number }

const { data: newUser } = await api.users.post({
  name: "Kai",
  email: "kai@example.com",
});
//    ^? { id: string, name: string, email: string, createdAt: Date }

const { error } = await api.users({ id: "bad-id" }).delete();
//    ^? { message: string } | null

// src/app.ts — Elysia with plugins
import { Elysia } from "elysia";
import { cors } from "@elysiajs/cors";
import { swagger } from "@elysiajs/swagger";
import { jwt } from "@elysiajs/jwt";

const app = new Elysia()
  .use(cors())
  .use(swagger({
    documentation: {
      info: { title: "My API", version: "1.0.0" },
    },
  }))
  .use(jwt({
    name: "jwt",
    secret: process.env.JWT_SECRET!,
    exp: "7d",
  }))
  // Auth guard as derive
  .derive(async ({ jwt, headers, error }) => {
    const token = headers.authorization?.replace("Bearer ", "");
    if (!token) return { user: null };
    const payload = await jwt.verify(token);
    if (!payload) return { user: null };
    return { user: payload as { id: string; email: string } };
  })
  // Protected route
  .get("/me", ({ user, error }) => {
    if (!user) return error(401, { message: "Not authenticated" });
    return user;
  })
  .listen(3000);

export type App = typeof app;

// src/routes/users.ts — Route group with shared prefix and guards
import { Elysia, t } from "elysia";

export const usersRoutes = new Elysia({ prefix: "/users" })
  .get("/", () => listUsers())
  .get("/:id", ({ params }) => getUser(params.id), {
    params: t.Object({ id: t.String() }),
  })
  .post("/", ({ body }) => createUser(body), {
    body: t.Object({
      name: t.String(),
      email: t.String({ format: "email" }),
    }),
  });

// Main app
import { Elysia } from "elysia";
import { usersRoutes } from "./routes/users";

const app = new Elysia()
  .use(usersRoutes)
  .listen(3000);