Which javascript framework(ex. Angular,Backbone,etc) you prefer to build your website and why you choose it?

As you talking about javascript frameworks. i would use MEAN STACK

M - MONGO DB

E- EXPRESS.JS

A- ANGULAR.JS

N- NODE JS

Express is a minimal and flexible web framework for Node inspired by Sinatra, a Ruby framework focused on HTTP routing. Most notably, Express is responsible for providing the Web API that empowers the MEAN stack.

MongoDB, Express, AngularJS, and Node.js work really well together. That's why i choose this because its fast and awesome for the real time applications as well as for other. if i have chance to work on it i would love.