The following APIs are the same as the native Web APIS you already know. We also follow the WinterCG (opens in a new tab) conventions. Lagon's Runtime uses the V8 engine and is written in both Rust and TypeScript.

Handler

The only required code to make your Function runnable is to export a handler function, that accepts a Request and returns a Response (or a promise returning a Response):

export function handler(request: Request) {
  return new Response('Hello World!');
}

Starting from this simple code, you can do whatever you wish, using the Web APIs you already know.

Additional Headers

The Request object coming from the handler function also contains additional headers:

• X-Lagon-Region: the region where this Function is executing
• X-Forwarded-For: the IP address of the client that made the request

You can access them the same as any other header:

export function handler(request: Request) {
  const region = request.headers.get('x-lagon-region');
  const ip = request.headers.get('x-forwarded-for');
 
  return new Response(`Region: ${region}, User IP: ${ip}`);
}

The X-Lagon-Region header is also automatically added to each response, making it easy to identify which Region served the request.

NPM support

Lagon's Runtime supports any NPM package. The only requirement is that the package must not use Node.js-specific APIs (e.g Buffer, fs, path, etc.). This is because Lagon's Runtime is not Node.js, but a browser-like environment.

Global objects

AbortController

The standard AbortController object. See the documentation on MDN (opens in a new tab).

AbortSignal

The standard AbortSignal object. See the documentation on MDN (opens in a new tab).

AsyncContext

An early implementation of the Async Context proposal (opens in a new tab). You shouldn't use this API yet, as it is still experimental and subject to change.

AsyncLocalStorage

A minimal implementation of Node.js's AsyncLocalStorage (opens in a new tab). The following methods are supported:

• getStore()
• run(store, callback, ...args)

Blob

The standard Blob object. See the documentation on MDN (opens in a new tab).

console

Similar to the standard console object on the browser and Node.js, except that it only supports the following methods:

• log
• info
• debug
• warn
• error

You can log multiple objects, and use string substitution. See the documentation on MDN (opens in a new tab).

crypto

The standard crypto object.

crypto.randomUUID()

The standard randomUUID() method. See the documentation on MDN (opens in a new tab).

crypto.getRandomValues()

The standard getRandomValues() method. See the documentation on MDN (opens in a new tab).

crypto.subtle

The standard CryptoSubtle object. See the documentation on MDN (opens in a new tab).

CustomEvent

The standard CustomEvent object. See the documentation on MDN (opens in a new tab).

Event

The standard Event object. See the documentation on MDN (opens in a new tab).

EventTarget

The standard EventTarget object. See the documentation on MDN (opens in a new tab).

Fetch APIs

Headers

The standard Headers object. It also supports the getSetCookie() method (opens in a new tab). See the documentation on MDN (opens in a new tab).

Request

The standard Request object. See the documentation on MDN (opens in a new tab).

Response

The standard Response object. See the documentation on MDN (opens in a new tab).

Streaming: You can pass a ReadableStream object as the body of a Response to stream the response as more data becomes available. Often, you won't need to implement the logic yourself as it is implemented by the frameworks and libraries you use.

URL

The standard URL object. See the documentation on MDN (opens in a new tab).

URLSearchParams

The standard URLSearchParams object. See the documentation on MDN (opens in a new tab).

File

The standard File object. See the documentation on MDN (opens in a new tab).

FileReader

The standard FileReader object. See the documentation on MDN (opens in a new tab).

FormData

The standard FormData object. See the documentation on MDN (opens in a new tab).

navigator.userAgent

navigator.userAgent is a fixed string that can be used to detect the current runtime. Its value is always Lagon/VERSION, where VERSION is the current version of the Lagon Runtime.

process.env

The only usage of process is to access environment variables. By default, it will only contain the NODE_ENV variable, which is set to "production" when deployed, and to "development" when using lagon dev.

Learn more about environment variables.

ProgressEvent

The standard ProgressEvent object. See the documentation on MDN (opens in a new tab).

Stream APIs

ReadableStream

The standard ReadableStream object. See the documentation on MDN (opens in a new tab).

ReadableStreamDefaultReader

The standard ReadableStreamDefaultReader object. See the documentation on MDN (opens in a new tab).

TransformStream

The standard TransformStream object. See the documentation on MDN (opens in a new tab).

WritableStream

The standard WritableStream object. See the documentation on MDN (opens in a new tab).

WritableStreamDefaultWriter

The standard WritableStreamDefaultWriter object. See the documentation on MDN (opens in a new tab).

TextEncoder

The standard TextEncoder object. See the documentation on MDN (opens in a new tab).

TextDecoder

The standard TextDecoder object. See the documentation on MDN (opens in a new tab).

Global methods

atob()

The standard atob method. See the documentation on MDN (opens in a new tab).

btoa()

The standard btoa method. See the documentation on MDN (opens in a new tab).

clearInterval()

The standard clearInterval method. See the documentation on MDN (opens in a new tab).

clearTimeout()

The standard clearTimeout method. See the documentation on MDN (opens in a new tab).

fetch()

The standard fetch method. See the documentation on MDN (opens in a new tab).

queueMicrotask()

The standard queueMicrotask method. See the documentation on MDN (opens in a new tab).

setInterval()

The standard setInterval method. See the documentation on MDN (opens in a new tab).

setTimeout()

The standard setTimeout method. See the documentation on MDN (opens in a new tab).