elysia-sveltekit

A strictly type-safe server hook adapter for bridging the Elysia web framework with SvelteKit.

This adapter allows you to seamlessly integrate an Elysia backend directly into your SvelteKit application's hooks.server.ts. It provides a factory function that creates an Elysia app instance and automatically maps SvelteKit's RequestEvent context (like locals and platform) into Elysia's lifecycle.

Features

• Type-Safe Context Injection: Pass SvelteKit's locals, platform, or any custom data directly into your Elysia endpoints.
• No Global State: State is safely encapsulated within a factory closure using a WeakMap.
• Zero Boilerplate: Returns a native SvelteKit Handle function ready to be exported from hooks.server.ts.
• Native Types: Leverages SvelteKit's native @sveltejs/kit types.

Installation

bun add elysia elysia-sveltekit

Usage

1. Initialize the Adapter & Define your API

Create your Elysia application and define the context mapping. The sveltekit factory returns both the Elysia app and the SvelteKit hook.

// src/lib/server/api.ts
import { sveltekit } from "elysia-sveltekit";

// 1. Define the context you want to inject
interface MyContext {
  locals: App.Locals;
  platform: App.Platform;
}

// 2. Initialize the adapter
export const { app, hook: handleApi } = sveltekit<MyContext, "/api">(
  (event) => ({
    locals: event.locals,
    platform: event.platform,
  }),
  { prefix: "/api" }, // The path prefix your Elysia app will listen on
);

// 3. Build your API endpoints
export const api = app.get("/hello", ({ locals, platform }) => {
  return {
    message: "Hello from Elysia!",
    user: locals.user, // Strongly typed!
  };
});

2. Connect the SvelteKit Hook

In your SvelteKit hooks.server.ts, simply export the generated hook.

// src/hooks.server.ts
import { handleApi } from "$lib/server/api";
import type { Handle } from "@sveltejs/kit";

export const handle: Handle = handleApi;

License

MIT