> ## Documentation Index
> Fetch the complete documentation index at: https://number0-improve-contact.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# JavaScript

> Use iroh from Node.js via the iroh-ffi bindings.

| Platform | Architectures                            |
| -------- | ---------------------------------------- |
| macOS    | arm64                                    |
| Linux    | x86\_64, aarch64 (glibc and musl), armv7 |
| Windows  | x86\_64, aarch64                         |
| Android  | aarch64, armv7                           |

All platforms require Node.js 20.3.0 or newer.

* **API reference:** [JavaScript API docs](https://n0-computer.github.io/iroh-ffi/js/)
* **Example app:** [hello-iroh-ffi](https://github.com/n0-computer/hello-iroh-ffi/tree/main/js), a console reader for the cross-platform dot demo
* **All languages:** [platform support matrix](/languages#platform-support)

The JavaScript bindings to iroh are published on npm as [`@number0/iroh`](https://www.npmjs.com/package/@number0/iroh) and shipped from [iroh-ffi](https://github.com/n0-computer/iroh-ffi). They're built with [napi-rs](https://napi.rs/), so the package distributes prebuilt native binaries. No Rust toolchain or local compilation is needed.

## Install

```bash theme={null}
npm install @number0/iroh
```

Requires Node.js 20.3.0 or newer. Prebuilt N-API binaries are published for:

* macOS: `arm64` (no Intel build)
* Linux: `x86_64` and `aarch64` (glibc + musl), `armv7` (gnueabihf + musleabihf)
* Windows: `x86_64` and `aarch64`
* Android: `aarch64` and `armv7`

## Hello, iroh

```javascript theme={null}
import { Endpoint } from '@number0/iroh'

const ALPN = Array.from(Buffer.from('hello-iroh/0'))

const ep = await Endpoint.bind({ alpns: [ALPN] })
console.log('endpoint id:', ep.id().toString())
await ep.close()
```

`Endpoint.bind` applies the `n0` preset (public discovery + default relays) by default. Pass an `EndpointOptions` object to override the preset, supply a fixed secret key, or set ALPNs.

## A two-peer echo

A minimal sender/receiver pair over a bidirectional stream:

```javascript theme={null}
// main.mjs: run `node main.mjs receiver` or `node main.mjs sender <ticket>`
import { Endpoint, EndpointTicket } from '@number0/iroh'

const ALPN = Array.from(Buffer.from('hello-iroh/0'))

async function receiver() {
  const ep = await Endpoint.bind({ alpns: [ALPN] })
  console.log('ticket:', EndpointTicket.fromAddr(ep.addr()).toString())

  const incoming = await ep.acceptNext()
  const conn = await (await incoming.accept()).connect()
  const bi = await conn.acceptBi()
  const msg = await bi.recv.readToEnd(1024)
  await bi.send.writeAll(msg)
  await bi.send.finish()
  await ep.close()
}

async function sender(ticketStr) {
  const ep = await Endpoint.bind()
  const addr = EndpointTicket.fromString(ticketStr).endpointAddr()
  const conn = await ep.connect(addr, ALPN)

  const bi = await conn.openBi()
  await bi.send.writeAll(Array.from(Buffer.from('hello')))
  await bi.send.finish()
  const echoed = await bi.recv.readToEnd(1024)
  console.log('echoed:', Buffer.from(echoed).toString('utf8'))
  await ep.close()
}

const [cmd, arg] = process.argv.slice(2)
if (cmd === 'receiver') await receiver()
else if (cmd === 'sender') await sender(arg)
else console.error('usage: receiver | sender <ticket>')
```

Start the receiver in one terminal, copy the printed ticket, and run the sender with it in another.

## Next steps

<Card title="Connect two endpoints" icon="rocket" href="/connect-two-endpoints" horizontal>
  Walkthrough of endpoints, tickets, and ALPNs with code samples in every language.
</Card>

<Card title="hello-iroh-ffi example app" icon="github" href="https://github.com/n0-computer/hello-iroh-ffi/tree/main/js" horizontal>
  A headless Node peer for the cross-platform dot demo. It speaks the same wire format as the Swift and Kotlin apps and prints received positions to the console.
</Card>

<Card title="JavaScript API reference" icon="book" href="https://n0-computer.github.io/iroh-ffi/js/" horizontal>
  Generated TypeDoc reference for `@number0/iroh`.
</Card>

<Card title="iroh-ffi on GitHub" icon="github" href="https://github.com/n0-computer/iroh-ffi" horizontal>
  Source, examples, and issue tracker for the JavaScript (and other-language) bindings.
</Card>