making a web request from within an isolate

On the Deno blog, Roll your own JavaScript runtime shows you how to write a JavaScript runtime, based on the V8 JavaScript engine, using parts of Deno. The example code can read and write to files and has a simplified console API.

This repository builds on that runtime and adds a global object called request that lets you make GET/POST web requests from within the runtime.

The bindings for request are set up in runtime/src/main.rs and runtime/src/minijs.js.

e.g.

const getExample = await request.get("http://healeycodes.com", {
  "someHeaderKey": "someHeaderValue",
});
console.log({
  status: getExample.status,
  headers: getExample.headers,
  url: getExample.url,
  body: getExample.body,
});

I'm not super familiar with the Deno project, so I've only worked on this enough to get it working – I'm not using Denoisms like zero-copy, etc.

HTTP Server

There's also a HTTP server that accepts user code and evaluates it within the runtime.

So to play around, you can run the server with cargo run and then send some code like curl -X POST -d 'console.log(await request.get("https://healeycodes.com", {}));' localhost:3000. console.log prints to the server's stdout.

Errors are returned to the client e.g. curl -X POST -d 'unknown;' localhost:3000 sends back ReferenceError: unknown is not defined at at ...

For real production example, look at how Deno's fetch function is setup: https://github.com/denoland/deno/tree/main/ext/fetch

Run

Run the server: cd runtime && cargo run

Send some code: curl -X POST -d 'unknown;' localhost:3000