Question

我可以在Android Chrome，macOS Chrome，Safari和Windows Chrome上使用“工作者”服务下载网站，以供离线使用。当我尝试将网站下载到 iOS 12.1 Safari 时，它将首先运行。但是，当我关闭Safari，脱机并重新打开Safari时，会收到以下错误消息：

Safari无法打开网站。

错误：“ FetchEvent.respondWith收到错误：TypeError：存在   似乎与互联网没有任何联系。”

====控制台中的AND ====

FetchEvent.respondWith收到错误：返回的响应为空

在下面，您可以以文本形式查看脚本。不幸的是，我几乎无法报告任何有关该问题的信息，因为我不理解它，希望有一些知识渊博的人：）

index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h1>Offline App</h1>
</body>
<script>
    if('serviceWorker' in navigator) {
        navigator.serviceWorker.register('sw.js').then(function (registration) {
            console.log('Service Worker Registered');
        });
    }
</script>
</html>

sw.js

/*
 Copyright 2014 Google Inc. All Rights Reserved.
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
 http://www.apache.org/licenses/LICENSE-2.0
 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
*/

importScripts('cache-polyfill.js');

var CACHE_VERSION = 1;
var CURRENT_CACHES = {
    prefetch: 'prefetch-cache-v' + CACHE_VERSION
};

self.addEventListener('install', function(event) {
    var now = Date.now();

    var urlsToPrefetch = [
        '/pwa/index.html'
    ];

    console.log('Handling install event. Resources to prefetch:', urlsToPrefetch);

    event.waitUntil(
        caches.open(CURRENT_CACHES.prefetch).then(function(cache) {
            var cachePromises = urlsToPrefetch.map(function(urlToPrefetch) {
                var url = new URL(urlToPrefetch, location.href);
                url.search += (url.search ? '&' : '?') + 'cache-bust=' + now;

                var request = new Request(url, {mode: 'no-cors'});
                return fetch(request).then(function(response) {
                    if (response.status >= 400) {
                        throw new Error('request for ' + urlToPrefetch +
                            ' failed with status ' + response.statusText);
                    }

                    return cache.put(urlToPrefetch, response);
                }).catch(function(error) {
                    console.error('Not caching ' + urlToPrefetch + ' due to ' + error);
                });
            });

            return Promise.all(cachePromises).then(function() {
                console.log('Pre-fetching complete.');
            });
        }).catch(function(error) {
            console.error('Pre-fetching failed:', error);
        })
    );
});

self.addEventListener('activate', function(event) {
    var expectedCacheNames = Object.keys(CURRENT_CACHES).map(function(key) {
        return CURRENT_CACHES[key];
    });

    event.waitUntil(
        caches.keys().then(function(cacheNames) {
            return Promise.all(
                cacheNames.map(function(cacheName) {
                    if (expectedCacheNames.indexOf(cacheName) === -1) {
                        console.log('Deleting out of date cache:', cacheName);
                        return caches.delete(cacheName);
                    }
                })
            );
        })
    );
});

self.addEventListener('fetch', function(event) {
    if (!navigator.onLine) {

        event.respondWith(
            caches.match(event.request).then(function (response) {
                if (response) {

                    return response;
                }

                console.log('No response found in cache. About to fetch from network...');

                return fetch(event.request).then(function (response) {
                    console.log('Response from network is:', response);

                    return response;
                }).catch(function (error) {
                    console.error('Fetching failed:', error);
                    throw error;
                });
            })
        );
    }
});