Integration with Next.js

With Next.js App Router, we can run Elysia on Next.js routes.

1. Create app/api/[[...slugs]]/route.ts
2. define an Elysia server
3. Export Elysia.fetch name of HTTP methods you want to use

app/api/[[...slugs]]/route.ts

import { Elysia, t } from 'elysia'

const app = new Elysia({ prefix: '/api' })
    .get('/', 'Hello Nextjs')
    .post('/', ({ body }) => body, {
        body: t.Object({
            name: t.String()
        })
    })

export const GET = app.fetch 
export const POST = app.fetch 

Elysia will work normally because of WinterTC compliance.

You can treat the Elysia server as a normal Next.js API route.

With this approach, you can have co-location of both frontend and backend in a single repository and have End-to-end type safety with Eden with both client-side and server action

Prefix

Because our Elysia server is not in the root directory of the app router, you need to annotate the prefix to the Elysia server.

For example, if you place Elysia server in app/user/[[...slugs]]/route.ts, you need to annotate prefix as /user to Elysia server.

app/user/[[...slugs]]/route.ts

import { Elysia, t } from 'elysia'

const app = new Elysia({ prefix: '/user' }) 
	.get('/', 'Hello Nextjs')
    .post('/', ({ body }) => body, {
        body: t.Object({
            name: t.String()
        })
    })

export const GET = app.fetch
export const POST = app.fetch

This will ensure that Elysia routing will work properly in any location you place it.

Eden

We can add Eden for end-to-end type safety similar to tRPC.

In this approach, we will use isomorphic fetch pattern to allow Elysia to:

1. On Server: directly calls Elysia without going through the network layer
2. On Client: calls Elysia through the network layer

To start, we need to do the following steps:

1. Export Elysia instance

app/api/[[...slugs]]/route.ts

import { Elysia } from 'elysia'

export const app = new Elysia({ prefix: '/api' }) 
	.get('/', 'Hello Nextjs')
	.post(
		'/user',
		({ body }) => body,
		{
			body: treaty.schema('User', {
				name: 'string'
			})
		}
	)

export const GET = app.fetch
export const POST = app.fetch

2. Create a Treaty client with isomorphic approach

lib/eden.ts

import { treaty } from '@elysiajs/eden'
import type { app } from '../app/api/[[...slugs]]/route'

// .api to enter /api prefix
export const api =
  typeof process !== 'undefined'
    ? treaty(app).api
    : treaty<typeof app>('localhost:3000').api

3. Use the client in both server and client components

app/page.tsx

import { api } from '../lib/eden'

export default async function Page() {
	const message = await api.get()

	return <h1>Hello, {message}</h1>
}

This allows you to have type safety from the frontend to the backend with minimal effort and works with both server, client components and with Incremental Static Regeneration (ISR).

Please refer to Next.js Route Handlers for more information.