Macro ​

A reusable route options.

Imagine we have an authentication check like this:

typescript
import { Elysia, t } from 'elysia'

new Elysia()
	.post('/user', ({ body }) => body, {
		cookie: t.Object({
			session: t.String()
		}),
		beforeHandle({ cookie: { session } }) {
			if(!session.value) throw 'Unauthorized'
		}
	})
	.listen(3000)

If we have multiple routes that require authentication, we have to repeat the same options over and over again.

Instead, we can use a macro to reuse route options:

typescript
import { Elysia, t } from 'elysia'

new Elysia()
	.macro('auth', {
		cookie: t.Object({
			session: t.String()
		}),
		// psuedo auth check
		beforeHandle({ cookie: { session }, status }) {
			if(!session.value) return status(401)
		}
	})
	.post('/user', ({ body }) => body, {
		auth: true
	})
	.listen(3000)

auth will then inline both cookie, and beforeHandle to the route.

Simply put, Macro is a reusable route options, similar to function but as a route options with type soundness.

Assignment ​

Let's define a macro to check if a body is a fibonacci number:

typescript
function isFibonacci(n: number) {
	let a = 0, b = 1
	while(b < n) [a, b] = [b, a + b]
	return b === n || n === 0
}

  1. Enforce Body Schema

    Let's enforce a schema as body for POST `/` endpoint that accept a number.

  2. Check if body is in Fibonacci Sequence

    We can use `isFibonacci` function to check if the number is in Fibonacci sequence. If it is not, return 418 status

Show answer
  1. To enforce type, we can define a body property in the macro.
  2. To short-circuit the request, we can use status function to return early.
typescript
import { Elysia, t } from 'elysia'

function isPerfectSquare(x: number) {
    const s = Math.floor(Math.sqrt(x))
    return s * s === x
}

function isFibonacci(n: number) {
    if (n < 0) return false

    return isPerfectSquare(5 * n * n + 4) || isPerfectSquare(5 * n * n - 4)
}

new Elysia()
    .macro('isFibonacci', {
		body: t.Number(),
        beforeHandle({ body, status }) {
            if(!isFibonacci(body)) return status(418)
        }
    })
	.post('/fibo', ({ body }) => body, {
		isFibonacci: true
	})
    .listen(3000)

  • index.ts