student-client/serviceWorkerAppend.js

/** append by ecs */
// 以下为学生端添加内容
console.log("sw printing before chrome58StopHere");
var stop = true;
(function() {
  try {
    Function("var a = {...{}};");
    stop = false;
  } catch (error) {
    console.log(error);
  }
})();
console.log("sw printing after chrome58StopHere ", stop);

// chrome 58 这个会报错，所以不执行
if (!stop) {
  self.addEventListener("fetch", event => {
    // Prevent the default, and handle the request ourselves.
    if (
      event.request.url.startsWith(
        "https://ecs-test-static.qmth.com.cn/comm-ques-bank/dev/audio"
      ) ||
      event.request.url.startsWith(
        "https://ecs-static.qmth.com.cn/comm-ques-bank/prod/audio/"
      )
    ) {
      event.respondWith(
        (async function() {
          // console.log("fetch intercepted");
          // Try to get the response from a cache.
          const cachedResponse = await caches.match(event.request);
          // Return it if we found one.
          if (cachedResponse) {
            console.log("cache res", event.request.url);
            return cachedResponse;
          }

          console.log("fetch audio intercept, try to load all");
          const res = await fetch(event.request.url);

          const reader = res.body.getReader();

          // Step 2: get total length
          const contentLength = +res.headers.get("Content-Length");

          if (contentLength === 0) {
            return fetch(event.request);
          }

          // Step 3: read the data
          let receivedLength = 0; // received that many bytes at the moment
          let chunks = []; // array of received binary chunks (comprises the body)
          // eslint-disable-next-line
          while (true) {
            const { done, value } = await reader.read();

            if (done) {
              break;
            }

            chunks.push(value);
            receivedLength += value.length;

            // console.log(`Received ${receivedLength} of ${contentLength}`);

            self.clients.matchAll().then(function(clients) {
              if (clients && clients.length) {
                clients.forEach(function(client) {
                  client.postMessage([
                    event.request.url,
                    receivedLength,
                    contentLength,
                  ]);
                });
              }
            });
          }

          // Step 4: concatenate chunks into single Uint8Array
          // let chunksAll = new Uint8Array(receivedLength); // (4.1)
          // let position = 0;
          // for (let chunk of chunks) {
          //   chunksAll.set(chunk, position); // (4.2)
          //   position += chunk.length;
          // }

          // const blob = await res.clone().blob();
          // const blob = new Blob([chunksAll.buffer]);
          const blob = new Blob(chunks);
          const responseFinal = new Response(blob, {
            headers: {
              "Content-Type": "audio/mp3",
              "Content-Length": contentLength,
            },
          });

          caches.open("audios").then(function(cache) {
            cache.put(event.request, responseFinal.clone());
          });

          return responseFinal.clone();
          // If we didn't find a match in the cache, use the network.
          // return fetch(event.request);
        })()
      );
    }
  });
}
console.log("sw printing end");