Runtimes & Languages

Invoke supports multiple languages and runtimes. Every function you create targets one language and runtime combination.

Supported Runtimes

Language	Runtime	SDK / Package
JavaScript	Bun	Built-in globals (kv, fetch, Router, RealtimeNamespace)
TypeScript	Bun	invoke-types (type definitions only)
C#	.NET 10 (NativeAOT)	Invoke.SDK NuGet package

Function Types

Each language supports three function types:

Type	Description
Simple Function	Handles all requests with a single entry point handler
Multi-Route App	Handles multiple routes with a router (HTTP method + path matching)
Realtime Handler	Handles Socket.IO-style events over a persistent WebSocket namespace

Function Signatures

JavaScript

Simple Function

export default async function handler(req, res) {
  res.json({ message: 'Hello, World!' })
}

Multi-Route App

const router = new Router()

router.get('/', (req, res) => res.json({ ok: true }))
router.get('/users/:id', (req, res) => res.json({ id: req.params.id }))
router.post('/users', async (req, res) => res.status(201).json(req.body))

export default router

Realtime Handler

const ns = new RealtimeNamespace('/chat')

ns.socket.on('$connect', function () {
  ns.socket.join('lobby')
})

ns.socket.on('message', function (data) {
  ns.socket.to('lobby').emit('message', data)
})

export default ns

TypeScript

Simple Function

export default async function handler(req: InvokeRequest, res: InvokeResponse) {
  res.json({ message: 'Hello, World!' })
}

Multi-Route App

const router = new Router()

router.get('/', (req: InvokeRequest, res: InvokeResponse) => res.json({ ok: true }))
router.get('/users/:id', (req: InvokeRequest, res: InvokeResponse) => res.json({ id: req.params.id }))
router.post('/users', async (req: InvokeRequest, res: InvokeResponse) => res.status(201).json(req.body))

export default router

Realtime Handler

const ns = new RealtimeNamespace('/chat')

ns.socket.on('$connect', function () {
  ns.socket.join('lobby')
})

ns.socket.on('message', function (data: { text: string }) {
  ns.socket.to('lobby').emit('message', data)
})

export default ns

C#

Simple Function

using Invoke;
using System.Text.Json.Nodes;

public static class Function
{
    [EntryPoint]
    public static Task EntryPoint(InvokeRequest req, InvokeResponse res)
    {
        res.Status(200).Json(new JsonObject { ["message"] = "Hello, World!" });
        return Task.CompletedTask;
    }
}

Multi-Route App

using Invoke;
using System.Text.Json.Nodes;

[EntryPoint]
public partial class App : Router
{
    [HttpGet("/")]
    public Task Index(InvokeRequest req, InvokeResponse res)
    {
        res.Status(200).Json(new JsonObject { ["ok"] = true });
        return Task.CompletedTask;
    }

    [HttpGet("/users/:id")]
    public Task GetUser(InvokeRequest req, InvokeResponse res)
    {
        res.Status(200).Json(new JsonObject { ["id"] = req.Params["id"] });
        return Task.CompletedTask;
    }

    [HttpPost("/users")]
    public Task CreateUser(InvokeRequest req, InvokeResponse res)
    {
        res.Status(201).Json(req.Body);
        return Task.CompletedTask;
    }
}

Realtime Handler

using Invoke;
using System.Text.Json.Nodes;

[EntryPoint]
public partial class App : RealtimeNamespace
{
    public App()
    {
        Namespace = "/chat";
    }

    [RealtimeEvent("$connect")]
    public async Task OnConnect(JsonNode arg)
    {
        await To("lobby").Emit("joined", new JsonObject { ["id"] = SocketId });
    }

    [RealtimeEvent("message")]
    public async Task OnMessage(JsonNode arg)
    {
        await To("lobby").Emit("message", arg);
    }
}

Project Structure

JavaScript

my-function/
├── index.js        # Entry point (exports default handler or router)
└── package.json    # Package config (type: "module")

package.json:

{
  "name": "my-function",
  "version": "1.0.0",
  "type": "module",
  "main": "index.js"
}

TypeScript

my-function/
├── index.ts        # Entry point
├── tsconfig.json   # TypeScript config
└── package.json    # Package config

package.json:

{
  "name": "my-function",
  "version": "1.0.0",
  "type": "module",
  "main": "index.ts",
  "devDependencies": {
    "invoke-types": "^1.0.0",
    "typescript": "^5.0.0"
  }
}

C#

my-function/
├── Function.cs     # Entry point (or App.cs for router/realtime)
└── app.csproj      # .NET project file

app.csproj:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net10.0</TargetFramework>
    <Nullable>enable</Nullable>
    <ImplicitUsings>enable</ImplicitUsings>
    <PublishAot>true</PublishAot>
    <InvariantGlobalization>true</InvariantGlobalization>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Invoke.SDK" Version="1.*" />
  </ItemGroup>
</Project>

Choosing a Runtime

Scenario	Recommended
Quick scripting, prototyping	JavaScript (Bun)
Type-safe functions, npm ecosystem	TypeScript (Bun)
High-performance, type-safe, low latency	C# (.NET)

See the API Reference for full Bun API documentation, or the .NET API Reference for the C# SDK.