我有一个由sw-precache生成的服务工作者，我正在页面上注册。安装和激活事件都成功触发和完成，文件被缓存，页面上的注册成功完成，但是fetch事件永远不会触发。根据我的阅读，这通常是由于服务工作者范围之外的请求被引起，但是范围是应用程序根（我可以从注册调用返回的注册对象中看到），以及所有来源包含在内。我尝试过不同的引用文件的方法，但行为总是一样的。我在Chrome和Firefox中也获得了相同的结果。除了范围之外，任何关于除了范围之外的什么的想法都会导致获取不被触发？
更新：所涉及的代码特别无益......
if("serviceWorker" in navigator) {
navigator.serviceWorker.register("ServiceWorker.js").then(function(registration) {
console.log("Service Worker installed successfully.", registration);
}).catch(function(err) {
console.log("Service Worker registration failed: " + err);
});
}
服务工作者是由sw-precache生成的，并且太长而无法完全放在这里，但这里是相关的听众：
self.addEventListener('install', function(event) {
event.waitUntil(
caches.open(cacheName).then(function(cache) {
return setOfCachedUrls(cache).then(function(cachedUrls) {
return Promise.all(
Array.from(urlsToCacheKeys.values()).map(function(cacheKey) {
// If we don't have a key matching url in the cache already, add it.
if (!cachedUrls.has(cacheKey)) {
var request = new Request(cacheKey, {credentials: 'same-origin'});
return fetch(request).then(function(response) {
// Bail out of installation unless we get back a 200 OK for
// every request.
if (!response.ok) {
throw new Error('Request for ' + cacheKey + ' returned a ' +
'response with status ' + response.status);
}
return cleanResponse(response).then(function(responseToCache) {
return cache.put(cacheKey, responseToCache);
});
});
}
})
);
});
}).then(function() {
// Force the SW to transition from installing -> active state
return self.skipWaiting();
})
);
});
self.addEventListener('activate', function(event) {
var setOfExpectedUrls = new Set(urlsToCacheKeys.values());
event.waitUntil(
caches.open(cacheName).then(function(cache) {
return cache.keys().then(function(existingRequests) {
return Promise.all(
existingRequests.map(function(existingRequest) {
if (!setOfExpectedUrls.has(existingRequest.url)) {
return cache.delete(existingRequest);
}
})
);
});
}).then(function() {
return self.clients.claim();
})
);
});
self.addEventListener('fetch', function(event) {
console.log("Fetch!");
if (event.request.method === 'GET') {
// Should we call event.respondWith() inside this fetch event handler?
// This needs to be determined synchronously, which will give other fetch
// handlers a chance to handle the request if need be.
var shouldRespond;
// First, remove all the ignored parameters and hash fragment, and see if we
// have that URL in our cache. If so, great! shouldRespond will be true.
var url = stripIgnoredUrlParameters(event.request.url, ignoreUrlParametersMatching);
shouldRespond = urlsToCacheKeys.has(url);
// If shouldRespond is false, check again, this time with 'index.html'
// (or whatever the directoryIndex option is set to) at the end.
var directoryIndex = 'index.html';
if (!shouldRespond && directoryIndex) {
url = addDirectoryIndex(url, directoryIndex);
shouldRespond = urlsToCacheKeys.has(url);
}
// If shouldRespond is still false, check to see if this is a navigation
// request, and if so, whether the URL matches navigateFallbackWhitelist.
var navigateFallback = '';
if (!shouldRespond &&
navigateFallback &&
(event.request.mode === 'navigate') &&
isPathWhitelisted([], event.request.url)) {
url = new URL(navigateFallback, self.location).toString();
shouldRespond = urlsToCacheKeys.has(url);
}
// If shouldRespond was set to true at any point, then call
// event.respondWith(), using the appropriate cache key.
if (shouldRespond) {
event.respondWith(
caches.open(cacheName).then(function(cache) {
return cache.match(urlsToCacheKeys.get(url)).then(function(response) {
if (response) {
return response;
}
throw Error('The cached response that was expected is missing.');
});
}).catch(function(e) {
// Fall back to just fetch()ing the request if some unexpected error
// prevented the cached response from being valid.
console.warn('Couldn\'t serve response for "%s" from cache: %O', event.request.url, e);
return fetch(event.request);
})
);
}
}
});
毋庸置疑，“抓取！”永远不会在控制台中显示。