sample-worker-interceptor.js

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importScripts('/common/get-host-info.sub.js');

const text = 'worker loading intercepted by service worker';

const dedicated_worker_script = `postMessage('${text}');`;

const shared_worker_script =

    `onconnect = evt => evt.ports[0].postMessage('${text}');`;

let source;

let resolveDone;

let done = new Promise(resolve => resolveDone = resolve);

// The page messages this worker to ask for the result. Keep the worker alive

// via waitUntil() until the result is sent.

self.addEventListener('message', event => {

  source = event.data.port;

  source.postMessage({id: event.source.id});

  source.onmessage = resolveDone;

  event.waitUntil(done);

});

self.onfetch = event => {

  const url = event.request.url;

  const destination = event.request.destination;

  if (source)

     source.postMessage({clientId:event.clientId, resultingClientId: event.resultingClientId});

  // Request handler for a synthesized response.

  if (url.indexOf('synthesized') != -1) {

    let script_headers = new Headers({ "Content-Type": "text/javascript" });

    if (destination === 'worker')

      event.respondWith(new Response(dedicated_worker_script, { 'headers': script_headers }));

    else if (destination === 'sharedworker')

      event.respondWith(new Response(shared_worker_script, { 'headers': script_headers }));

    else

      event.respondWith(new Response('Unexpected request! ' + destination));

    return;

  // Request handler for a same-origin response.

  if (url.indexOf('same-origin') != -1) {

    event.respondWith(fetch('postmessage-on-load-worker.js'));

    return;

  // Request handler for a cross-origin response.

  if (url.indexOf('cors') != -1) {

    const filename = 'postmessage-on-load-worker.js';

    const path = (new URL(filename, self.location)).pathname;

    let new_url = get_host_info()['HTTPS_REMOTE_ORIGIN'] + path;

    let mode;

    if (url.indexOf('no-cors') != -1) {

      // Test no-cors mode.

      mode = 'no-cors';

    } else {

      // Test cors mode.

      new_url += '?pipe=header(Access-Control-Allow-Origin,*)';

      mode = 'cors';

    event.respondWith(fetch(new_url, { mode: mode }));

};