I am creating a offline first blogging platform which utilises IndexedDB and service workers. The idea here is if the user is offline and trying to send a post - send it in the background. This project is for my dissertation, I have only been looking at promises for a week or so - apologies if it is a simple error!
From my action in react/redux, i'm sending the sync event through successfully.
Below is the code for my sync event handler
self.addEventListener('sync', function(event) {
if (event.tag == 'send_post') {
//const URL
console.log('sync from SW - send post');
//this should try again if promise is rejected
event.waitUntil(
openDatabase('Outbox').then( (db) => {
return databaseGet('posts',db).then( (posts) => {
return sendAllFromOutbox(posts)
} )
} )
);
}
});
Below is openDatabase - (IndexedDB)
function openDatabase(name) {
return new Promise(function(resolve, reject) {
var version = 10;
var request = indexedDB.open(name, version);
var db;
request.onupgradeneeded = function(e) {
db = e.target.result;
e.target.transaction.onerror = reject;
};
request.onsuccess = function(e) {
db = e.target.result;
console.log('OPENED DATABASE');
resolve(db);
};
request.onerror = reject;
});
}
Below is databaseGet
function databaseGet(type,db) {
return new Promise(function(resolve, reject) {
var transaction = db.transaction([type], 'readonly');
var store = transaction.objectStore(type);
var request = store.getAll();
request.onsuccess = function(e) {
var result = e.target.result;
resolve(result);
};
request.onerror = reject;
});
}
And finally, below is sendAllFromOutbox
function sendAllFromOutbox(posts) {
return fetch('https://stirapi.herokuapp.com/sendPost', {
headers: {'Content-Type': 'application/json'},
method: "POST",
body: JSON.stringify(posts)
})
.then( (response) => {
console.log('response from SW sendAllFromOutbox', response);
} )
.catch( (err) => {
console.log('error from SW sendAllFromOutbox',err);
} )
}
From my understanding, if sendAllFromOutbox fails/rejects - it should get called again. But it doesn't seem to be getting called - and therefore is not being sent in the background.
If you would like to check out my repo - it's here https://github.com/georgecook92/Stir.
Thank you!
George
