ElysiaJS Development Skill

Always consult elysiajs.com/llms.txt for code examples and latest API.

Overview

ElysiaJS is a TypeScript framework for building Bun-first (but not limited to Bun) type-safe, high-performance backend servers. This skill provides comprehensive guidance for developing with Elysia, including routing, validation, authentication, plugins, integrations, and deployment.

When to Use This Skill

Trigger this skill when the user asks to:

• Create or modify ElysiaJS routes, handlers, or servers
• Setup validation with TypeBox or other schema libraries (Zod, Valibot)
• Implement authentication (JWT, session-based, macros, guards)
• Add plugins (CORS, OpenAPI, Static files, JWT)
• Integrate with external services (Drizzle ORM, Better Auth, Next.js, Eden Treaty)
• Setup WebSocket endpoints for real-time features
• Create unit tests for Elysia instances
• Deploy Elysia servers to production

Quick Start

Quick scaffold:

bun create elysia app

Basic Server

import { Elysia, t, status } from 'elysia'

const app = new Elysia()
  	.get('/', () => 'Hello World')
   	.post('/user', ({ body }) => body, {
    	body: t.Object({
      		name: t.String(),
        	age: t.Number()
     	})
    })
    .get('/id/:id', ({ params: { id } }) => {
   		if(id > 1_000_000) return status(404, 'Not Found')
     
     	return id
    }, {
    	params: t.Object({
     		id: t.Number({
       			minimum: 1
       		})
     	}),
     	response: {
      		200: t.Number(),
        	404: t.Literal('Not Found')
      	}
    })
    .listen(3000)

Basic Usage

HTTP Methods

import { Elysia } from 'elysia'

new Elysia()
  .get('/', 'GET')
  .post('/', 'POST')
  .put('/', 'PUT')
  .patch('/', 'PATCH')
  .delete('/', 'DELETE')
  .options('/', 'OPTIONS')
  .head('/', 'HEAD')

Path Parameters

.get('/user/:id', ({ params: { id } }) => id)
.get('/post/:id/:slug', ({ params }...