TODO Offline-first App

This is a website that you can log tasks and it will save our any number of apps.

Installation

Download files and run:

npm install

This project uses mysql. Put your mysql database settings in config/config.json. The table name must be tasks.

Features

• background sync
• works with multiple devices
• offline use
• multiple devices
• service workers
• postMessage
• mySQL
• node + express
• JAWSDB
• indexedDB

Mysql database structure

This app uses synco and syncoff objectstores. Entries that are not synced to remote mysql database are placed in syncoff until sync happens. -columns: id, name, changed, status, date_created,date_updated

status - can only have none(default), deleted

How the Synchronization Works

Each entry has a changed column, defaults to 1 When the user clicks the sync button, all columns that have changed of 1 are changed to a value of 0 and added to the online database. If the user is offline, as soon at the user has internet connection, the sync will happen.

Clicking on an entry will "delete" the entry make it invisible. status changes to deleted. status is none by default.

how much data is sent to indexeddb

there is no limit to the amount of data on indexeddb but there is a 5 mb restriction on the JAWSDB because I am using free subscription. Contact theshagod@gmail.com if you this product is useful and would like to see more development.

Syncing method order

1. get new entries in mysql by comparing id numbers add to var entries and add to synco
2. open syncoff and synco
3. get offline entries and add to var entries and add to synco
4. get changed entries in synco and add to var entries (with ids so it puts instad of adds in mysql) and PUT to synco
5. add var entries to mysql
6. clear syncoff and send postMessage to client that transaction is complete so that it can postMessage to let client know to render the list again

References

• Very useful indexeddb resource: https://developer.mozilla.org/en-US/docs/Web/API/IndexedDB_API/Using_IndexedDB
• The single most useful link about using postmessage with service workers: https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorkerGlobalScope/message_event

Note to self

When deploying don't forget to use process.env.PORT || hardportnumberhere or heroku will crash. Source: https://stackoverflow.com/questions/14322989/first-heroku-deploy-failed-error-code-h10