Eden Treaty

Eden Treaty is an object representation to interact with a server and features type safety, auto-completion, and error handling.

To use Eden Treaty, first export your existing Elysia server type:

// server.ts
import { Elysia, t } from 'elysia'

const app = new Elysia()
    .get('/hi', () => 'Hi Elysia')
    .get('/id/:id', ({ params: { id } }) => id)
    .post('/mirror', ({ body }) => body, {
        body: t.Object({
            id: t.Number(),
            name: t.String()
        })
    })
    .listen(3000)

export type App = typeof app // [!code ++]

Then import the server type and consume the Elysia API on the client:

// @filename: server.ts
import { Elysia, t } from 'elysia'

const app = new Elysia()
    .get('/hi', () => 'Hi Elysia')
    .get('/id/:id', ({ params: { id } }) => id)
    .post('/mirror', ({ body }) => body, {
        body: t.Object({
            id: t.Number(),
            name: t.String()
        })
    })
    .listen(3000)

export type App = typeof app // [!code ++]

// @filename: client.ts
// ---cut---
// client.ts
import { treaty } from '@elysiajs/eden'
import type { App } from './server' // [!code ++]

const app = treaty<App>('localhost:3000')

// response type: 'Hi Elysia'
const { data, error } = await app.hi.get()
      // ^?

Tree like syntax

HTTP Path is a resource indicator for a file system tree.

File system consists of multiple levels of folders, for example:

• /documents/elysia
• /documents/kalpas
• /documents/kelvin

Each level is separated by / (slash) and a name.

However in JavaScript, instead of using "/" (slash) we use "." (dot) to access deeper resources.

Eden Treaty turns an Elysia server into a tree-like file system that can be accessed in the JavaScript frontend instead.

Combined with the HTTP method, we can interact with the Elysia server.

Dynamic path

However, dynamic path parameters cannot be expressed using notation. If they are fully replaced, we don't know what the parameter name is supposed to be.

// ❌ Unclear what the value is supposed to represent?
treaty.item['skadi'].get()

To handle this, we can specify a dynamic path using a function to provide a key value instead.

// ✅ Clear that value is dynamic path is 'name'
treaty.item({ name: 'Skadi' }).get()