Elysia.js

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Error Handling ​

Elysia catches all the errors thrown in the handler, classifies the error code, and pipes them to onError middleware.

typescript
new Elysia()
    .get('/', () => {
        throw new Error('Server is during maintainance')
        
        return 'unreachable'
    })
    .onError(({ code, error }) => {
        return new Response(error.toString())
    })

new Elysia()
    .get('/', () => {
        throw new Error('Server is during maintainance')
        
        return 'unreachable'
    })
    .onError(({ code, error }) => {
        return new Response(error.toString())
    })

With onError you can catch and transform the error into your custom error message.

For example, returning custom 404 messages:

typescript
import { Elysia } from 'elysia'

new Elysia()
    .onError(({ code, error, set }) => {
        if (code === 'NOT_FOUND') {
            set.status = 404
        
            return 'Not Found :('
        }
    })
    .listen(8080)

import { Elysia } from 'elysia'

new Elysia()
    .onError(({ code, error, set }) => {
        if (code === 'NOT_FOUND') {
            set.status = 404
        
            return 'Not Found :('
        }
    })
    .listen(8080)

Local Error ​

You can assign error handling method to a scope using hook or guard

typescript
app.get('/', () => 'Hello', {
    beforeHandle: ({ set, request: { headers } }) => {
        if(!isSignIn(headers)) {
            set.status = 401
            return 'Unauthorized'
        }
    }
})

app.get('/', () => 'Hello', {
    beforeHandle: ({ set, request: { headers } }) => {
        if(!isSignIn(headers)) {
            set.status = 401
            return 'Unauthorized'
        }
    }
})

Error Code ​

Elysia error code consists of:

  • NOT_FOUND
  • INTERNAL_SERVER_ERROR
  • VALIDATION
  • UNKNOWN

By default, user thrown error code is unknown.

TIP

If no error response is returned, the error will be returned using error.name.