# Node.js & Bun

> Source: `src/content/docs/clients/javascript.mdx`
> Canonical URL: https://rivet.dev/docs/clients/javascript
> Description: Connect JavaScript apps to Rivet Actors.

---
## Getting Started

See the [backend quickstart guide](/docs/actors/quickstart/backend) for getting started.

## Minimal Client

```ts client.ts
import { createClient } from "rivetkit/client";
import type { registry } from "./index";

const client = createClient<typeof registry>({
  endpoint: "https://my-namespace:pk_...@api.rivet.dev",
});
const counter = client.counter.getOrCreate(["my-counter"]);
const count = await counter.increment(1);
```

```ts index.ts @hide
import { actor, setup } from "rivetkit";

export const counter = actor({
  state: { count: 0 },
  actions: {
    increment: (c, x: number) => {
      c.state.count += x;
      return c.state.count;
    },
  },
});

export const registry = setup({
  use: { counter },
});

registry.start();
```

## Stateless vs Stateful

```typescript
import { createClient } from "rivetkit/client";

const client = createClient();
const handle = client.counter.getOrCreate(["my-counter"]);

// Stateless: each call is independent
await handle.increment(1);

// Stateful: keep a connection open for realtime events
const conn = handle.connect();
conn.on("count", (value) => console.log(value));
await conn.increment(1);
```

## Getting Actors

```typescript
import { createClient } from "rivetkit/client";

const client = createClient();
const room = client.chatRoom.getOrCreate(["room-42"]);
const existing = client.chatRoom.get(["room-42"]);

const created = await client.game.create(["game-1"], {
  input: { mode: "ranked" },
});

const byId = client.chatRoom.getForId("actor-id");
const resolvedId = await room.resolve();
```

## Connection Parameters

```typescript params
import { createClient } from "rivetkit/client";

const client = createClient();
const chat = client.chatRoom.getOrCreate(["general"], {
  params: { authToken: "jwt-token-here" },
});

const conn = chat.connect();
```

```typescript getParams
import { createClient } from "rivetkit/client";

async function getAuthToken(): Promise<string> {
  return "jwt-token-here";
}

const client = createClient();
const chat = client.chatRoom.getOrCreate(["general"], {
  getParams: async () => ({
    authToken: await getAuthToken(),
  }),
});

const conn = chat.connect();
```

Use `params` for static connection parameters. Use `getParams` when the value can change between connection attempts, such as refreshing a JWT before each `.connect()` or reconnect.

## Subscribing to Events

```typescript
import { createClient } from "rivetkit/client";

const client = createClient();
const conn = client.chatRoom.getOrCreate(["general"]).connect();
conn.on("message", (msg) => console.log(msg));
conn.once("gameOver", () => console.log("done"));
```

## Connection Lifecycle

```typescript
import { createClient } from "rivetkit/client";

const client = createClient();
const conn = client.chatRoom.getOrCreate(["general"]).connect();

conn.onOpen(() => console.log("connected"));
conn.onClose(() => console.log("disconnected"));
conn.onError((err) => console.error("error:", err));
conn.onStatusChange((status) => console.log("status:", status));

await conn.dispose();
```

## Low-Level HTTP & WebSocket

For actors that implement `onRequest` or `onWebSocket`, call them directly:

```ts @nocheck
import { createClient } from "rivetkit/client";

const client = createClient();
const handle = client.chatRoom.getOrCreate(["general"]);

const response = await handle.fetch("history");
const history = await response.json();

const ws = await handle.webSocket("stream");
ws.addEventListener("message", (event) => {
  console.log("message:", event.data);
});
ws.send("hello");
```

## Calling from Backend

```typescript
import { Hono } from "hono";
import { createClient } from "rivetkit/client";

const app = new Hono();
const client = createClient();

app.post("/increment/:name", async (c) => {
  const counterHandle = client.counter.getOrCreate([c.req.param("name")]);
  const newCount = await counterHandle.increment(1);
  return c.json({ count: newCount });
});
```

## Error Handling

```typescript
import { ActorError } from "rivetkit/client";
import { createClient } from "rivetkit/client";

const client = createClient();

try {
  await client.user.getOrCreate(["user-123"]).updateUsername("ab");
} catch (error) {
  if (error instanceof ActorError) {
    console.log(error.code, error.metadata);
  }
}
```

## Concepts

### Keys

Keys uniquely identify actor instances. Use compound keys (arrays) for hierarchical addressing:

```ts client.ts
import { createClient } from "rivetkit/client";
import type { registry } from "./index";

const client = createClient<typeof registry>("http://localhost:6420");

// Compound key: [org, room]
client.chatRoom.getOrCreate(["org-acme", "general"]);
```

```ts index.ts @hide
import { actor, setup } from "rivetkit";

export const chatRoom = actor({
  state: { messages: [] as string[] },
  actions: {
    getRoomInfo: (c) => ({ org: c.key[0], room: c.key[1] }),
  },
});

export const registry = setup({
  use: { chatRoom },
});

registry.start();
```

Don't build keys with string interpolation like `"org:${userId}"` when `userId` contains user data. Use arrays instead to prevent key injection attacks.

### Environment Variables

`createClient()` automatically reads:

- `RIVET_ENDPOINT` (endpoint)
- `RIVET_NAMESPACE`
- `RIVET_TOKEN`
- `RIVET_RUNNER`

Defaults to `http://localhost:6420` when unset. RivetKit runs on port 6420 by default.

### Endpoint Format

Endpoints support URL auth syntax:

```
https://namespace:token@api.rivet.dev
```

You can also pass the endpoint without auth and provide `RIVET_NAMESPACE` and `RIVET_TOKEN` separately. For serverless deployments, use your app's `/api/rivet` URL. See [Endpoints](/docs/general/endpoints#url-auth-syntax) for details.

## Advanced

### Skip Ready Wait

Requests are normally held at the gateway until the actor is ready to accept traffic. An actor is not ready while it's still starting (before `onWake` finishes) or while it's in the [sleep grace period](/docs/actors/lifecycle#shutdown-sequence) (running `onSleep`, `waitUntil`, and pending disconnects).

Pass `skipReadyWait: true` on the [low-level HTTP and WebSocket APIs](#low-level-http--websocket) to deliver immediately and reach the actor's `onRequest` / `onWebSocket` handler in either window:

```ts @nocheck
import { createClient } from "rivetkit/client";

const client = createClient();
const handle = client.chatRoom.getOrCreate(["general"]);

const response = await handle.fetch("/healthz", {
  skipReadyWait: true,
});

const ws = await handle.webSocket("probe", undefined, {
  skipReadyWait: true,
});
```

Requests can still return transient lifecycle or gateway errors. Retry once the actor is available again.

- `actor.stopping`: the actor has fully stopped, i.e. the sleep grace period has ended but it has not yet restarted.
- `guard.actor_stopped_while_waiting`: the request reached the actor tunnel, but the actor stopped before the gateway received a response.
- `guard.tunnel_request_aborted`: the actor tunnel aborted the request before a response started.
- `guard.tunnel_message_timeout`: the gateway dropped the in-flight tunnel request after its tunnel message timeout.
- `guard.tunnel_response_closed`: the actor tunnel closed before sending a response.
- `guard.gateway_response_start_timeout`: the gateway timed out waiting for the actor response to start.

## API Reference

**Package:** [rivetkit](https://www.npmjs.com/package/rivetkit)

See the [RivetKit client overview](/docs/clients).

- [`createClient`](/typedoc/functions/rivetkit.client_mod.createClient.html) - Create a client
- [`Client`](/typedoc/types/rivetkit.mod.Client.html) - Client type

_Source doc path: /docs/clients/javascript_
