var requests = []; var port = undefined; self.onmessage = function(e) { var message = e.data; if ('port' in message) { port = message.port; port.postMessage({ready: true}); } }; self.addEventListener('fetch', function(event) { var url = event.request.url; if (url.indexOf('dummy?test') == -1) { return; } port.postMessage({ url: url, mode: event.request.mode, credentials: event.request.credentials, integrity: event.request.integrity }); event.respondWith(Promise.reject()); });