处理文件上传/删除以及几乎所有事情的一种方法是跟踪脱机请求期间所做的所有更改。我们可以创建一个sync对象内部有两个数组，一个用于需要上传的待处理文件，一个用于需要在我们重新上线时删除的已删除文件。
tl;dr
关键阶段
-
Service Worker 安装
-
服务人员获取
-
Syncing
代码实现
(Please read the inline comments)
服务人员安装
const cacheName = 'pwasndbx';
const syncCacheName = 'pwasndbx-sync';
const pendingName = '__pending';
const syncName = '__sync';
const filesToCache = [
'/',
'/uploads',
'/styles.css',
'/main.js',
'/utils.js',
'/favicon.ico',
'/manifest.json',
];
/* Start the service worker and cache all of the app's content */
self.addEventListener('install', function(e) {
console.log('SW:install');
e.waitUntil(Promise.all([
caches.open(cacheName).then(async function(cache) {
let cacheAdds = [];
try {
// Get all the files from the uploads listing
const res = await fetch('/uploads');
const { data = [] } = await res.json();
const files = data.map(f => `/uploads/${f}`);
// Cache all uploads files urls
cacheAdds.push(cache.addAll(files));
} catch(err) {
console.warn('PWA:install:fetch(uploads):err', err);
}
// Also add our static files to the cache
cacheAdds.push(cache.addAll(filesToCache));
return Promise.all(cacheAdds);
}),
// Create the sync cache object
caches.open(syncCacheName).then(cache => cache.put(syncName, jsonResponse({
pending: [], // For storing the penging files that later will be synced
deleted: [] // For storing the files that later will be deleted on sync
}))),
])
);
});
服务人员获取
self.addEventListener('fetch', function(event) {
// Clone request so we can consume data later
const request = event.request.clone();
const { method, url, headers } = event.request;
event.respondWith(
fetch(event.request).catch(async function(err) {
const { headers, method, url } = event.request;
// A custom header that we set to indicate the requests come from our syncing method
// so we won't try to fetch anything from cache, we need syncing to be done on the server
const xSyncing = headers.get('X-Syncing');
if(xSyncing && xSyncing.length) {
return caches.match(event.request);
}
switch(method) {
case 'GET':
// Handle listing data for /uploads and return JSON response
break;
case 'PUT':
// Handle upload to cache and return success response
break;
case 'DELETE':
// Handle delete from cache and return success response
break;
}
// If we meet no specific criteria, then lookup to the cache
return caches.match(event.request);
})
);
});
function jsonResponse(data, status = 200) {
return new Response(data && JSON.stringify(data), {
status,
headers: {'Content-Type': 'application/json'}
});
}
服务人员获取Listing GET
if(url.match(/\/uploads\/?$/)) { // Failed to get the uploads listing
// Get the uploads data from cache
const uploadsRes = await caches.match(event.request);
let { data: files = [] } = await uploadsRes.json();
// Get the sync data from cache
const syncRes = await caches.match(new Request(syncName), { cacheName: syncCacheName });
const sync = await syncRes.json();
// Return the files from uploads + pending files from sync - deleted files from sync
const data = files.concat(sync.pending).filter(f => sync.deleted.indexOf(f) < 0);
// Return a JSON response with the updated data
return jsonResponse({
success: true,
data
});
}
服务人员获取上传中PUT
// Get our custom headers
const filename = headers.get('X-Filename');
const mimetype = headers.get('X-Mimetype');
if(filename && mimetype) {
// Get the uploads data from cache
const uploadsRes = await caches.match('/uploads', { cacheName });
let { data: files = [] } = await uploadsRes.json();
// Get the sync data from cache
const syncRes = await caches.match(new Request(syncName), { cacheName: syncCacheName });
const sync = await syncRes.json();
// If the file exists in the uploads or in the pendings, then return a 409 Conflict response
if(files.indexOf(filename) >= 0 || sync.pending.indexOf(filename) >= 0) {
return jsonResponse({ success: false }, 409);
}
caches.open(cacheName).then(async (cache) => {
// Write the file to the cache using the response we cloned at the beggining
const data = await request.blob();
cache.put(`/uploads/${filename}`, new Response(data, {
headers: { 'Content-Type': mimetype }
}));
// Write the updated files data to the uploads cache
cache.put('/uploads', jsonResponse({ success: true, data: files }));
});
// Add the file to the sync pending data and update the sync cache object
sync.pending.push(filename);
caches.open(syncCacheName).then(cache => cache.put(new Request(syncName), jsonResponse(sync)));
// Return a success response with fromSw set to tru so we know this response came from service worker
return jsonResponse({ success: true, fromSw: true });
}
服务人员获取正在删除DELETE
// Get our custom headers
const filename = headers.get('X-Filename');
if(filename) {
// Get the uploads data from cache
const uploadsRes = await caches.match('/uploads', { cacheName });
let { data: files = [] } = await uploadsRes.json();
// Get the sync data from cache
const syncRes = await caches.match(new Request(syncName), { cacheName: syncCacheName });
const sync = await syncRes.json();
// Check if the file is already pending or deleted
const pendingIndex = sync.pending.indexOf(filename);
const uploadsIndex = files.indexOf(filename);
if(pendingIndex >= 0) {
// If it's pending, then remove it from pending sync data
sync.pending.splice(pendingIndex, 1);
} else if(sync.deleted.indexOf(filename) < 0) {
// If it's not in pending and not already in sync for deleting,
// then add it for delete when we'll sync with the server
sync.deleted.push(filename);
}
// Update the sync cache
caches.open(syncCacheName).then(cache => cache.put(new Request(syncName), jsonResponse(sync)));
// If the file is in the uplods data
if(uploadsIndex >= 0) {
// Updates the uploads data
files.splice(uploadsIndex, 1);
caches.open(cacheName).then(async (cache) => {
// Remove the file from the cache
cache.delete(`/uploads/${filename}`);
// Update the uploads data cache
cache.put('/uploads', jsonResponse({ success: true, data: files }));
});
}
// Return a JSON success response
return jsonResponse({ success: true });
}
Synching
// Get the sync data from cache
const syncRes = await caches.match(new Request(syncName), { cacheName: syncCacheName });
const sync = await syncRes.json();
// If the are pending files send them to the server
if(sync.pending && sync.pending.length) {
sync.pending.forEach(async (file) => {
const url = `/uploads/${file}`;
const fileRes = await caches.match(url);
const data = await fileRes.blob();
fetch(url, {
method: 'PUT',
headers: {
'X-Filename': file,
'X-Syncing': 'syncing' // Tell SW fetch that we are synching so to ignore this fetch
},
body: data
}).catch(err => console.log('sync:pending:PUT:err', file, err));
});
}
// If the are deleted files send delete request to the server
if(sync.deleted && sync.deleted.length) {
sync.deleted.forEach(async (file) => {
const url = `/uploads/${file}`;
fetch(url, {
method: 'DELETE',
headers: {
'X-Filename': file,
'X-Syncing': 'syncing' // Tell SW fetch that we are synching so to ignore this fetch
}
}).catch(err => console.log('sync:deleted:DELETE:err', file, err));
});
}
// Update and reset the sync cache object
caches.open(syncCacheName).then(cache => cache.put(syncName, jsonResponse({
pending: [],
deleted: []
})));
示例 PWA
我创建了一个实现所有这些的 PWA 示例，您可以找到并测试它here https://pwasndbx.zikro.gr/。我已经使用 Chrome 和 Firefox 以及在移动设备上使用 Firefox Android 对其进行了测试。
您可以找到该应用程序的完整源代码（包括一个express server）在此 Github 存储库中：https://github.com/clytras/pwa-sandbox https://github.com/clytras/pwa-sandbox.
