Aggregate requests

/**
 * someHost is set up to return JSON responses
 * Replace url1 and url2 with the hosts you wish to send requests to
 * @param {string} url the URL to send the request to
 */
const someHost = 'https://examples.cloudflareworkers.com/demos';
const url1 = someHost + '/requests/json';
const url2 = someHost + '/requests/json';
const type = 'application/json;charset=UTF-8';

/**
 * gatherResponse awaits and returns a response body as a string.
 * Use await gatherResponse(..) in an async function to get the response body
 * @param {Response} response
 */
async function gatherResponse(response) {
  const { headers } = response;
  const contentType = headers.get('content-type') || '';
  if (contentType.includes('application/json')) {
    return JSON.stringify(await response.json());
  } else if (contentType.includes('application/text')) {
    return response.text();
  } else if (contentType.includes('text/html')) {
    return response.text();
  } else {
    return response.text();
  }
}

async function handleRequest() {
  const init = {
    headers: {
      'content-type': type,
    },
  };
  const responses = await Promise.all([fetch(url1, init), fetch(url2, init)]);
  const results = await Promise.all([gatherResponse(responses[0]), gatherResponse(responses[1])]);
  return new Response(results.join(), init);
}

addEventListener('fetch', event => {
  return event.respondWith(handleRequest());
});