Read and write JSON file for mobile app - html

Question

I am working on a mobile app. Since I wanted a solution that would work on multiple platforms, I started with Cordova. As I have much data to handle and many views, I decided to use Ember.
I need to use three different JSON datasets that are updated rather frequently in the database. To enable the mobile app to work offline, I will have to store the JSON data, as well as update them when the database is changed.
Questions
How can I retrieve JSON from another server(CORS blocked)?
How can the retrieved JSON be saved on device? [HTML5 LocalStorage(preferred) or FileAPI]
How to read JSON file and send data as model to templates? (I guess Ember.$.getJSON can do this)
Any help is welcome. Thanks!
Update 1
Since I ran into many issues using Ember-data, I am not using it in my app.
Found this link for cross-domain with ajax
Update 2
CORS can be solved only by JSONP or by setting ACCESS-CONTROL-ALLOW-ORIGIN in the reponse of the server(I tried many other solutions, and failed)
Since the api is in my server, I did the latter.
For 2 and 3, I think I could use this SO question

Answer 1

This is what I found out :
JSON data from a server in different domain
You cannot read JSON data from a server in another domain. This is due to the Same-origin policy implemented in browsers. A browser will retrieve your JSON but will not allow you access to the same. There are two solutions(AFAIK) to this problem :
Using JSONP - I'm not going into the details, but there are many links available for this.
Allow CORS from server - When the server sends JSONified data, you can add additional headers for ACCESS-CONTROL-ALLOW-ORIGIN. After retrieving the JSON from server, the browser checks for this header to either block or allow CORS. I used some decorators for adding crossdomain headers and then my data was successfully read in the browser.
Saving the json data
HTML5 makes everything easier. In your javascript, you just have to use :
localStorage["application.state.data"] = JSON.stringify(json);
or
localStorage.setItem("application.state.data", JSON.stringify(json));
Retrieve works just the same
var data = JSON.parse(localStorage["application.state.data"]);
or
var data = JSON.parse(localStorage.getItem("application.state.data"));