http-hello-world.js

/**
 * This module is the JS implementation of the `component` WIT world
 */

import {
  ResponseOutparam,
  OutgoingBody,
  OutgoingResponse,
  Fields,
} from 'wasi:http/types@0.2.4';

/**
 * This export represents the `wasi:http/incoming-handler` interface,
 * which describes implementing a HTTP handler in WebAssembly using WASI types.
 */
export const incomingHandler = {
  /**
   * This Javascript will be turned into a WebAssembly component by `jco` and turned into a
   * WebAssembly binary with a single export (this `handler` function).
   *
   * The exported `handle` method is part of the `wasi:http/incoming-handler` interface,
   * which defines how to hadle incoming web requests, turning this component into one that can
   * serve web requests.
   */
  handle(_incomingRequest, responseOutparam) {
    // Start building an outgoing response
    const outgoingResponse = new OutgoingResponse(new Fields());

    // Access the outgoing response body
    let outgoingBody = outgoingResponse.body();
    {
      // Create a stream for the response body
      let outputStream = outgoingBody.write();
      // Write hello world to the response stream
      outputStream.blockingWriteAndFlush(
        new Uint8Array(new TextEncoder().encode('Hello from Javascript!\n'))
      );
      // @ts-ignore: This is required in order to dispose the stream before we return
      outputStream[Symbol.dispose]();
    }

    // Set the status code for the response
    outgoingResponse.setStatusCode(200);
    // Finish the response body
    OutgoingBody.finish(outgoingBody, undefined);
    // Set the created response to an "OK" Result<T> value
    ResponseOutparam.set(responseOutparam, { tag: 'ok', val: outgoingResponse });
  }

};