Is it possible to build an application inside in browser? An application means:

1 Where there is connection (online mode) between the browser and an remote application server:

• the application runs in typical web-based mode
• the application stores necessary data in offline storage, to be used in offline mode (2)
• the application sync/push data (captured during offline mode) back to the server when it is resumed from offline mode back to online mode

2 Where there is no connection (offline mode) between the browser and an remote application server:

• the application will still run (javascript?)
• the application will present data (which is stored offline) to user
• the application can accept input from user (and store/append in offline storage)

Is this possible? If the answer is a yes, is there any (Ruby/Python/PHP) framework being built?

Thanks