Request

The first life-cycle event to get executed for every new request is recieved.

As onRequest is designed to provide only the most crucial context to reduce overhead, it is recommended to use in the following scenario:

• Caching
• Rate Limiter / IP/Region Lock
• Analytic
• Provide custom header, eg. CORS

Example

Below is a pseudo code to enforce rate-limit on a certain IP address.

import { Elysia } from 'elysia'

new Elysia()
    .use(rateLimiter)
    .onRequest(({ rateLimiter, ip, set }) => {
        if(rateLimiter.check(ip)) {
            set.status = 420
            return 'Enhance your calm'
        }
    })
    .get('/', () => 'hi')
    .listen(3000)

If a value is returned from onRequest, it will be used as the response and the rest of the life-cycle will be skipped.

Pre Context

Context's onRequest is typed as PreContext, a minimal representation of Context with the attribute on the following: request: Request

• set: Set
• store
• decorators

Context doesn't provide derived value because derive is based on onTransform event.