Building the web app with json only data with javascript and ORM
I'm working on a Django project for the past six months, where I'm using Django for the backend service, returning only json responses, and the frontend code is completely separate. 
jQuery by itself would result in unmaintainable code, even on a smaller scale, so you definitely need a high level frontend framework. I settled with Durandal.js, which includes:

Knockout.js for the ui bindings
Sammy.js for view routing
Require.js to modularize the code

I think it was a good choice at the time, and I feel very productive with that tech stack. If I were to start from scratch again, it would be very likely a similar stack.
As for ExtJS, it's a component/widget based framework, which philosophy I don't very much like, I saw the future, and it wasn't written in ExtJS :)
Although I see AngularJS and EmberJS as the titans that will very likely win the battle of  frameworks, at least for now.
I have given the new project to complete where i have separate components which talk to each other via services calls
They are not linked directly.
The technical head wants to build the entire frontend in ExtJS or jquery and then use JSON to load the data. I mean all forms , login etc will be JSON.
Now i ahve not done anything like that that. I mean i have always generated forms , data from server side controllers and views. like PHP or Django python.
I want to know that is this way good or achievable because i don't want to chnage things after spending time initially.
but is its the good way then i can start with it