Validation ​

Elysia offers data validation out of the box.

You can use Elysia.t to define a schema.

import { Elysia, t } from 'elysia'

new Elysia()
	.post(
		'/user',
		({ body: { name } }) => `Hello ${name}!`,
		{
			body: t.Object({
				name: t.String(),
				age: t.Number()
			})
		}
	)
	.listen(3000)

When you define a schema, Elysia will ensure the data is in a correct shape.

If the data doesn't match the schema, Elysia will return a 422 Unprocessable Entity error.

See Validation.

Bring your own ​

Alternatively, Elysia support Standard Schema, allowing you to use a library of your choice like zod, yup or valibot.

import { Elysia } from 'elysia'
import { z } from 'zod'

new Elysia()
	.post(
		'/user',
		({ body: { name } }) => `Hello ${name}!`,
		{
			body: z.object({
				name: z.string(),
				age: z.number()
			})
		}
	)
	.listen(3000)

See Standard Schema for all compatible schema.

Validation Type ​

You can validate the following property:

• body
• query
• params
• headers
• cookie
• response

Once schema is defined, Elysia will infers type for you so You don't have to define a separate schema in TypeScript.

See Schema Type for each type.

Response Validation ​

When you define a validation schema for response, Elysia will validate the response before sending it to the client, and type check the response for you.

You can also specify which status code to validate:

import { Elysia, t } from 'elysia'

new Elysia()
	.get(
		'/user',
		() => `Hello Elysia!`,
		{
			response: {
				200: t.Literal('Hello Elysia!'),
				418: t.Object({
					message: t.Literal("I'm a teapot")
				})
			}
		}
	)
	.listen(3000)

See Response Validation.

Assignment ​

Let's execrise what we have learned.

import { Elysia } from 'elysia'

new Elysia()
	.get('/', ({ status, set }) => {
		set.headers['x-powered-by'] = 'Elysia'

		return status(418, 'Hello Elysia!')
	})
	.get('/docs', ({ redirect }) => redirect('https://elysiajs.com'))
	.listen(3000)