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Eden Installation ​

Start by installing Eden on your frontend:

bash
bun add @elysiajs/eden
bun add -d elysia
bun add @elysiajs/eden
bun add -d elysia

TIP

Eden needs Elysia to infer utilities type.

Make sure to install Elysia with the version matching on the server.

First, export your existing Elysia server type:

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

const app = new Elysia()
    .get('/', () => 'Hi Elysia')
    .get('/id/:id', ({ params: { id } }) => id)
    .post('/mirror', ({ body }) => body, {
        body: t.Object({
            id: t.Number(),
            name: t.String()
        })
    })
    .listen(8080)

export type App = typeof app 
// server.ts
import { Elysia, t } from 'elysia'

const app = new Elysia()
    .get('/', () => 'Hi Elysia')
    .get('/id/:id', ({ params: { id } }) => id)
    .post('/mirror', ({ body }) => body, {
        body: t.Object({
            id: t.Number(),
            name: t.String()
        })
    })
    .listen(8080)

export type App = typeof app 

Then consume the Elysia API on client side:

typescript
// client.ts
import { edenTreaty } from '@elysiajs/eden'
import type { App } from './server' 

const client = edenTreaty<App>('http://localhost:8080') 

// response type: 'Hi Elysia'
client.index.get().then(console.log)

// response type: 1895
client.id[1895].get().then(console.log)

// response type: { id: 1895, name: 'Skadi' }
client.mirror.post({
    id: 1895,
    name: 'Skadi'
}).then(console.log)
// client.ts
import { edenTreaty } from '@elysiajs/eden'
import type { App } from './server' 

const client = edenTreaty<App>('http://localhost:8080') 

// response type: 'Hi Elysia'
client.index.get().then(console.log)

// response type: 1895
client.id[1895].get().then(console.log)

// response type: { id: 1895, name: 'Skadi' }
client.mirror.post({
    id: 1895,
    name: 'Skadi'
}).then(console.log)

Gotcha ​

Sometimes Eden may not infer type from Elysia correctly, the following are the most common workaround to fix Eden type inference.

Type Strict ​

Make sure to enable strict mode in tsconfig.json

json
{
  "compilerOptions": {
    "strict": true 
  }
}
{
  "compilerOptions": {
    "strict": true 
  }
}

Unmatch Elysia version ​

Eden depends Elysia class to import Elysia instance and infers type correctly.

Make sure that both client and server have a matching Elysia version.

TypeScript version ​

Elysia uses newer features and syntax of TypeScript to infer types in a the most performant way. Features like Const Generic and Template Literal are heavily used.

Make sure your client has a minimum TypeScript version if >= 5.0

Method Chaining ​

To make Eden works, Elysia must be using method chaining

Elysia's type system is complex, methods usually introduce a new type to the instance.

Using method chaining will help save that new type reference.

For example:

typescript
const app = new Elysia()
    .state('build', 1)
    // Store is strictly typed
    .get('/', ({ store: { build } }) => build)
    .listen(3000)
const app = new Elysia()
    .state('build', 1)
    // Store is strictly typed
    .get('/', ({ store: { build } }) => build)
    .listen(3000)

Using this, state now returns a new ElysiaInstance type, introducing build into store and replace the current one.

Without using method chaining, Elysia doesn't save the new type when introduced, leading to no type inference.

typescript
const app = new Elysia()

app.state('build', 1)

// Doesn't have access to build
app.get('/', ({ store: { build } }) => build)

app.listen(3000)
const app = new Elysia()

app.state('build', 1)

// Doesn't have access to build
app.get('/', ({ store: { build } }) => build)

app.listen(3000)

We recommend to always use method chaining to provide an accurate type inference.