Map Response

Executed just after "afterHandle", designed to provide custom response mapping.

It's recommended to use transform for the following:

• Compression
• Map value into a Web Standard Response

Example

Below is an example of using mapResponse to provide Response compression.

import { Elysia } from 'elysia'

const encoder = new TextEncoder()

new Elysia()
    .mapResponse(({ response, set }) => {
        const isJson = typeof response === 'object'

        const text = isJson
            ? JSON.stringify(response)
            : response?.toString() ?? ''

        set.headers['Content-Encoding'] = 'gzip'

        return new Response(
            Bun.gzipSync(encoder.encode(text)),
            {
                headers: {
                    'Content-Type': `${
                        isJson ? 'application/json' : 'text/plain'
                    }; charset=utf-8`
                }
            }
        )
    })
    .get('/text', () => 'mapResponse')
    .get('/json', () => ({ map: 'response' }))
    .listen(3000)

Like parse and beforeHandle, after a value is returned, the next iteration of mapResponse will be skipped.

Elysia will handle the merging process of set.headers from mapResponse automatically. We don't need to worry about appending set.headers to Response manually.