I have a simple forum that I want to make work offline. I have a dynamic and static cahce. The static cache fills on the install event and the dynamic as you go allong and look at posts.
The problem is that the pages it caches include the header where you have a link to the profile if you are logged in and link to registration page if you are not logged in.
After logging in it still shows the registration link instead of the profile link. The way to fix it would be to refresh the cache?
Is there a way to do this or is there some other fix for this type of issue(besides network first approach)?
I am relativly new to PWAs and I can't find any useful tips.
My service worker looks like this:
const staticCacheName = "ScroocCacheV1";
const dynamicCacheName = "ScroocDynamicCacheV1";
const assets = [
'/',
'/css/main_styles.css',
'/js/ui.js',
'/about',
'/policies',
'/register',
'/createTopic',
'/stats',
'/proposals',
];
const limitCacheSize = (name, size) => {
caches.open(name).then(cache => {
cache.keys().then(keys => {
if(keys.length > size) {
cache.delete(keys[0]).then(limitCacheSize(name, size));
}
});
});
}
const dynamicCacheLimit = 18;
// Install service worker
self.addEventListener('install', evt => {
evt.waitUntil(
caches.open(staticCacheName).then(cache => {
cache.addAll(assets);
})
);
});
// Activate event
self.addEventListener('activate', evt => {
evt.waitUntil(
caches.keys().then(keys => {
keys.map((key => {
if (key !== staticCacheName && key !== dynamicCacheName) {
return caches.delete(key); //Deleting the old cache (cache v1)
}
}))
})
)
});
// Intercept fetch
self.addEventListener('fetch', evt => {
evt.respondWith(
fetch(evt.request).then(fetchRes => {
return caches.open(dynamicCacheName).then(cache => {
return caches.match(evt.request).then(function(result) {
if (result) {
return result;
} else {
cache.put(evt.request.url, fetchRes.clone());
limitCacheSize(dynamicCacheName, dynamicCacheLimit);
return fetchRes;
}
});
});
}).catch(function() {
return caches.match(evt.request).catch((error) => {
console.log(error)
return caches.match('/img/fallbackImage.png');
});
})
);
});
This worked for me!
Before you could attempt to empty the cache, the service worker must first be successfully installed. So for the record, your sw.js file should begin with the usual
self.addEventListener("install", ...etc
Now this is where we get to cleaning up. Create a variable to store the name of the cache you wish to purge/update (makes targeting different caches easier)
var TargetCache= 'NameOfCacheToClean';
Next, add an EventListener that triggers each time the service worker is activated (the activate-event occurs on page reload/refresh)
self.addEventListener('activate', event =>
{
const currentCaches = [TargetCache];
event.waitUntil
(
caches.keys()
.then(cacheNames => {return cacheNames.filter(cacheName => !currentCaches.includes(cacheName));})
.then(cachesToDelete => {return Promise.all(cachesToDelete.map(cacheToDelete => {return caches.delete(cacheToDelete);})); })
.then(() => self.clients.claim())
);
});
Just in-case, i normally add the event listener that intercepts the outgoing fetch-requests after the code that clears the old cache.
self.addEventListener('fetch', function(event) {...etc
The way to fix it would be to refresh the cache?
That is correct, assuming you cached the path /login, the service worker will always display what was cached under that path, based on your code.
Is there a way to do this or is there some other fix for this type of issue(besides network first approach)?
It's not really something to "fix", what you described is somewhat expected behaviour.
There are several ways around this tho, network first is just one:
use a message to update cache on login
use different urls or url parts like query to skip cache when user is logged in
hide the UI that you don't need on the client depending on user state
Probably many more.
I can't get my service worker to work offline. No matter what tutorial I use.
I registered the service worker in my index.html file like:
<script>
if ('serviceWorker' in navigator) {
window.addEventListener('load', () => {
navigator.serviceWorker.register('/serviceworker.js')
.then((reg) => console.log('success: ', reg.scope))
.catch((err) => console.log('Failure: ', err))
})
}
</script>
The serviceworker.js looks like:
const CACHE_NAME = "version-1"
const urlsToCache = [ 'index.html' ]
const self = this
// Install Service Worker
self.addEventListener('install', (event) => {
event.waitUntil(
caches.open(CACHE_NAME)
.then((cache) => {
console.log('Opened cache')
return cache.addAll(urlsToCache)
})
)
})
// Activate Service Worker
self.addEventListener('activate', (event) => {
const cacheWhitelist = []
cacheWhitelist.push(CACHE_NAME)
event.waitUntil(
caches.keys().then((cacheNames) => Promise.all(
cacheNames.map((cacheName) => {
if(!cacheWhitelist.includes(cacheName)) {
return caches.delete(cacheName)
}
})
))
)
})
I'm not sure what I've forgotten or what mistake I have. The serviceworker.js is right beside the index.html, manifest.json etc.
I sometimes get an error with "An unknown error occured when fetching the script".
Kind regards
Your service worker only contains code to create a cache and store the HTML file in that local cache. This cache is managed by you, the browser does not care about it when fetching web pages normally.
When your browser fetches that index.html web page, it does not know about that cache. So what you need to do is to intercept that fetch. For this, you need to register an event listener for the fetch event and respond with your cache. The browser will then use that file instead of sending a request to the server.
self.addEventListener('fetch', event => {
if (event.request.method != 'GET') return;
event.respondWith(async function() {
const cache = await caches.open(CACHE_NAME);
const cached = await cache.match(event.request);
// If no cached version, fall back to server fetch
return cached ? cached : fetch(event.request);
})
});
I'm developing an audio-based PWA and, since I'm not familiar with this technology, I have a couple of doubts regading the cache management and invalidation in the service worker.
The application need to work offline, that I covered using a SW precache.
My only doubt is the amount of data: in the experience there are 5 use case scenarios. Each scenario has ~30MB of audio content, that means around 150MB + all images, js and css in total to precache.
I know that this exceeds the limit of some browsers (se this question and this article)
and in general you must be careful with the storage size, that also depends on the user's device available space on disk.
So that's what I thought: since between one scenario and another, the users will stop by a desk with WiFi connection, my idea is to empty the cache runtime after an user's action (like pressing a button), and replace it with thw new content.
This way I would store only one scenario at a time, that means ~35MB, a reasonable size.
Do you think that's a good approach?
What's the best way to implement this?
Here's my current code:
service-worker.js
const PRECACHE = 'precache-test-v1';
// A list of local resources we always want to be cached.
const PRECACHE_URLS = [
'/',
'/audio/scenario1.mp3',
'/audio/scenario2.mp3',
'/audio/scenario3.mp3',
'/audio/scenario4.mp3',
'/audio/scenario5.mp3',
'/css/style.css',
'/js/bundle.js',
'/img/favicon.png',
'/img/logo.png',
'/img/image1.png',
'/img/image2.png',
'/img/image3.png',
'/img/image4.png',
'/img/image5.png',
];
// never cache these resources
const TO_SKIP = [/* empty for now */];
// The install handler takes care of precaching the resources we always need.
self.addEventListener('install', event => {
const now = new Date();
console.log(`PWA Service Worker installing - :: ${now} ::`);
event.waitUntil(caches.open(PRECACHE).then(cache => {
return cache.addAll(PRECACHE_URLS).then(() => {
self.skipWaiting();
});
}));
});
// The activate handler takes care of cleaning up old caches.
self.addEventListener('activate', event => {
const now = new Date();
console.log(`PWA Service Worker activating - :: ${now} ::`);
const currentCaches = [PRECACHE];
event.waitUntil(
caches.keys().then(cacheNames => {
return cacheNames.filter(cacheName => !currentCaches.includes(cacheName));
}).then(cachesToDelete => {
return Promise.all(cachesToDelete.map(cacheToDelete => {
return caches.delete(cacheToDelete);
}));
}).then(() => self.clients.claim())
);
});
// The fetch handler serves responses for same-origin resources from a cache.
self.addEventListener('fetch', event => {
// Skip cross-origin requests, like those for Google Analytics and the other provided urls.
if (event.request.url.startsWith(self.location.origin) && TO_SKIP.every(url => !event.request.url.includes(url))) {
event.respondWith(
caches.match(event.request).then(resp => {
return resp || fetch(event.request).then(response => {
return caches.open(PRECACHE).then(cache => {
cache.put(event.request, response.clone());
return response;
});
});
})
);
}
});
index.js
if ('serviceWorker' in navigator) {
navigator.serviceWorker.register('/sw.js').then(registration => {
console.log('Registration successful, scope is:', registration.scope);
}).catch(error => {
console.log('Service worker registration failed, error:', error);
});
}
Thank you for your time,
Francesco
Hmm.. instead of precaching 5 videos, you could provide an button Save for offline so that the user can save only that videos that he wants to see later offline:
let videoUrl = url to that video:
button.addEventListener('click', function(event) {
event.preventDefault();
caches.open("myVideoCache").then(function(cache) {
fetch(videoUrl)
.then(function(video) {
cache.add(video);
});
});
});
Do delete 1 entry you need to open your cache and delete it. Pass the path that you stored.
caches.open('myVideoCache').then(function(cache) {
cache.delete('/path/to/audio.mp4').then(function(response) {
console.log("entry deleted");
});
})
More details you can find here: https://developers.google.com/web/ilt/pwa/caching-files-with-service-worker
We have a web app (built using AngularJS) that we're gradually adding PWA 'features' too (service worker, launchable, notifications, etc). One of the features our web app has is the ability to complete a web form while offline. At the moment, we store the data in IndexedDB when offline, and simply encourage the user to push that data to the server once they're online ("This form is saved to your device. Now you're back online, you should save it to the cloud..."). We will do this automatically at some point, but that's not necessary at the moment.
We are adding a feature to these web forms, whereby the user will be able to attach files (images, documents) to the form, perhaps at several points throughout the form.
My question is this - is there a way for service worker to handle file uploads? To somehow - perhaps - store the path to the file to be uploaded, when offline, and push that file up once the connection has been restored? Would this work on mobile devices, as do we have access to that 'path' on those devices? Any help, advice or references would be much appreciated.
When the user selects a file via an <input type="file"> element, we are able to get the selected file(s) via fileInput.files. This gives us a FileList object, each item in it being a File object representing the selected file(s). FileList and File are supported by HTML5's Structured Clone Algorithm.
When adding items to an IndexedDB store, it creates a structured clone of the value being stored. Since FileList and File objects are supported by the structured clone algorithm, this means that we can store these objects in IndexedDB directly.
To perform those file uploads once the user goes online again, you can use the Background Sync feature of service workers. Here's an introductory article on how to do that. There are a lot of other resources for that as well.
In order to be able to include file attachments in your request once your background sync code runs, you can use FormData. FormDatas allow adding File objects into the request that will be sent to your backend, and it is available from within the service worker context.
One way to handle file uploads/deletes and almost everything, is by keeping track of all the changes made during the offline requests. We can create a sync object with two arrays inside, one for pending files that will need to be uploaded and one for deleted files that will need to be deleted when we'll get back online.
tl;dr
Key phases
Service Worker Installation
Along with static data, we make sure to fetch dynamic data as the main listing of our uploaded files (in the example case /uploads GET returns JSON data with the files).
Service Worker Fetch
Handling the service worker fetch event, if the fetch fails, then we have to handle the requests for the files listing, the requests that upload a file to the server and the request that deletes a file from the server. If we don't have any of these requests, then we return a match from the default cache.
Listing GET
We get the cached object of the listing (in our case /uploads) and the sync object. We concat the default listing files with the pending files and we remove the deleted files and we return new response object with a JSON result as the server would have returned it.
Uloading PUT
We get the cached listing files and the sync pending files from the cache. If the file isn't present, then we create a new cache entry for that file and we use the mime type and the blob from the request to create a new Response object that it will be saved to the default cache.
Deleting DELETE
We check in the cached uploads and if the file is present we delete the entry from both the listing array and the cached file. If the file is pending we just delete the entry from the pending array, else if it's not already in the deleted array, then we add it. We update listing, files and sync object cache at the end.
Syncing
When the online event gets triggered, we try to synchronize with the server. We read the sync cache.
If there are pending files, then we get each file Response object from cache and we send a PUT fetch request back to the server.
If there are deleted files, then we send a DELETE fetch request for each file to the server.
Finally, we reset the sync cache object.
Code implementation
(Please read the inline comments)
Service Worker Install
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
}))),
])
);
});
Service Worker Fetch
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'}
});
}
Service Worker Fetch Listing GET
if(url.match(/\/uploads\/?$/)) { // Failed to get the uploads listing
// Get the uploads data from cache
const uploadsRes = await caches.match(event.request);
let { data: files = [] } = await uploadsRes.json();
// Get the sync data from cache
const syncRes = await caches.match(new Request(syncName), { cacheName: syncCacheName });
const sync = await syncRes.json();
// Return the files from uploads + pending files from sync - deleted files from sync
const data = files.concat(sync.pending).filter(f => sync.deleted.indexOf(f) < 0);
// Return a JSON response with the updated data
return jsonResponse({
success: true,
data
});
}
Service Worker Fetch Uloading PUT
// Get our custom headers
const filename = headers.get('X-Filename');
const mimetype = headers.get('X-Mimetype');
if(filename && mimetype) {
// Get the uploads data from cache
const uploadsRes = await caches.match('/uploads', { cacheName });
let { data: files = [] } = await uploadsRes.json();
// Get the sync data from cache
const syncRes = await caches.match(new Request(syncName), { cacheName: syncCacheName });
const sync = await syncRes.json();
// If the file exists in the uploads or in the pendings, then return a 409 Conflict response
if(files.indexOf(filename) >= 0 || sync.pending.indexOf(filename) >= 0) {
return jsonResponse({ success: false }, 409);
}
caches.open(cacheName).then(async (cache) => {
// Write the file to the cache using the response we cloned at the beggining
const data = await request.blob();
cache.put(`/uploads/${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 });
}
Service Worker Fetch Deleting 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: []
})));
Example PWA
I have created a PWA example that implements all these, which you can find and test here. I have tested it using Chrome and Firefox and using Firefox Android on a mobile device.
You can find the full source code of the application (including an express server) in this Github repository: https://github.com/clytras/pwa-sandbox.
The Cache API is designed to store a request (as the key) and a response (as the value) in order to cache a content from the server, for the web page. Here, we're talking about caching user input for future dispatch to the server. In other terms, we're not trying to implement a cache, but a message broker, and that's not currently something handled by the Service Worker spec (Source).
You can figure it out by trying this code:
HTML:
<button id="get">GET</button>
<button id="post">POST</button>
<button id="put">PUT</button>
<button id="patch">PATCH</button>
JavaScript:
if ('serviceWorker' in navigator) {
navigator.serviceWorker.register('/service-worker.js', { scope: '/' }).then(function (reg) {
console.log('Registration succeeded. Scope is ' + reg.scope);
}).catch(function (error) {
console.log('Registration failed with ' + error);
});
};
document.getElementById('get').addEventListener('click', async function () {
console.log('Response: ', await fetch('50x.html'));
});
document.getElementById('post').addEventListener('click', async function () {
console.log('Response: ', await fetch('50x.html', { method: 'POST' }));
});
document.getElementById('put').addEventListener('click', async function () {
console.log('Response: ', await fetch('50x.html', { method: 'PUT' }));
});
document.getElementById('patch').addEventListener('click', async function () {
console.log('Response: ', await fetch('50x.html', { method: 'PATCH' }));
});
Service Worker:
self.addEventListener('fetch', function (event) {
var response;
event.respondWith(fetch(event.request).then(function (r) {
response = r;
caches.open('v1').then(function (cache) {
cache.put(event.request, response);
}).catch(e => console.error(e));
return response.clone();
}));
});
Which throws:
TypeError: Request method 'POST' is unsupported
TypeError: Request method 'PUT' is unsupported
TypeError: Request method 'PATCH' is unsupported
Since, the Cache API can't be used, and following the Google guidelines, IndexedDB is the best solution as a data store for ongoing requests.
Then, the implementation of a message broker is the responsibility of the developer, and there is no unique generic implementation that will cover all of the use cases. There are many parameters that will determine the solution:
Which criteria will trigger the use of the message broker instead of the network? window.navigator.onLine? A certain timeout? Other?
Which criteria should be used to start trying to forward ongoing requests on the network? self.addEventListener('online', ...)? navigator.connection?
Should requests respect the order or should they be forwarded in parallel? In other terms, should they be considered as dependent on each other, or not?
If run in parallel, should they be batched to prevent a bottleneck on the network?
In case the network is considered available, but the requests still fail for some reason, which retry logic to implement? Exponential backoff? Other?
How to notify the user that their actions are in a pending state while they are?
...
This is really very broad for a single StackOverflow answer.
That being said, here is a minimal working solution:
HTML:
<input id="file" type="file">
<button id="sync">SYNC</button>
<button id="get">GET</button>
JavaScript:
if ('serviceWorker' in navigator) {
navigator.serviceWorker.register('/service-worker.js', { scope: '/' }).then(function (reg) {
console.log('Registration succeeded. Scope is ' + reg.scope);
}).catch(function (error) {
console.log('Registration failed with ' + error);
});
};
document.getElementById('get').addEventListener('click', function () {
fetch('api');
});
document.getElementById('file').addEventListener('change', function () {
fetch('api', { method: 'PUT', body: document.getElementById('file').files[0] });
});
document.getElementById('sync').addEventListener('click', function () {
navigator.serviceWorker.controller.postMessage('sync');
});
Service Worker:
self.importScripts('https://unpkg.com/idb#5.0.1/build/iife/index-min.js');
const { openDB, deleteDB, wrap, unwrap } = idb;
const dbPromise = openDB('put-store', 1, {
upgrade(db) {
db.createObjectStore('put');
},
});
const idbKeyval = {
async get(key) {
return (await dbPromise).get('put', key);
},
async set(key, val) {
return (await dbPromise).put('put', val, key);
},
async delete(key) {
return (await dbPromise).delete('put', key);
},
async clear() {
return (await dbPromise).clear('put');
},
async keys() {
return (await dbPromise).getAllKeys('put');
},
};
self.addEventListener('fetch', function (event) {
if (event.request.method === 'PUT') {
let body;
event.respondWith(event.request.blob().then(file => {
// Retrieve the body then clone the request, to avoid "body already used" errors
body = file;
return fetch(new Request(event.request.url, { method: event.request.method, body }));
}).then(response => handleResult(response, event, body)).catch(() => handleResult(null, event, body)));
} else if (event.request.method === 'GET') {
event.respondWith(fetch(event.request).then(response => {
return response.ok ? response : caches.match(event.request);
}).catch(() => caches.match(event.request)));
}
});
async function handleResult(response, event, body) {
const getRequest = new Request(event.request.url, { method: 'GET' });
const cache = await caches.open('v1');
await idbKeyval.set(event.request.method + '.' + event.request.url, { url: event.request.url, method: event.request.method, body });
const returnResponse = response && response.ok ? response : new Response(body);
cache.put(getRequest, returnResponse.clone());
return returnResponse;
}
// Function to call when the network is supposed to be available
async function sync() {
const keys = await idbKeyval.keys();
for (const key of keys) {
try {
const { url, method, body } = await idbKeyval.get(key);
const response = await fetch(url, { method, body });
if (response && response.ok)
await idbKeyval.delete(key);
}
catch (e) {
console.warn(`An error occurred while trying to sync the request: ${key}`, e);
}
}
}
self.addEventListener('message', sync);
Some words about the solution: it allows to cache the PUT request for future GET requests, and it also stores the PUT request into an IndexedDB database for future sync. About the key, I was inspired by Angular's TransferHttpCacheInterceptor which allows to serialize backend requests on the server-side rendered page for use by the browser-rendered page. It uses <verb>.<url> as the key. That supposes a request will override another request with the same verb and URL.
This solution also supposes that the backend does not return 204 No content as a response of a PUT request, but 200 with the entity in the body.
I was also stumbling upon it lately. Here is what I am doing to store in index db and return response when offline.
const storeFileAndReturnResponse = async function (request, urlSearchParams) {
let requestClone = request.clone();
let formData = await requestClone.formData();
let tableStore = "fileUploads";
let fileList = [];
let formDataToStore = [];
//Use formData.entries to iterate collection - this assumes you used input type= file
for (const pair of formData.entries()) {
let fileObjectUploaded = pair[1];
//content holds the arrayBuffer (blob) of the uploaded file
formDataToStore.push({
key: pair[0],
value: fileObjectUploaded,
content: await fileObjectUploaded.arrayBuffer(),
});
let fileName = fileObjectUploaded.name;
fileList.push({
fileName: fileName,
});
}
let payloadToStore = {
parentId: parentId,
fileList: fileList,
formDataKeyValue: formDataToStore,
};
(await idbContext).put(tableStore, payloadToStore);
return {
UploadedFileList: fileList,
};
};