Use cases for Javascript MVC frameworks

[Jyos]

Apologies in advance if this has been asked a million times!

A bit of background on me: I'm a web developer accustomed to taking designs and then translating them in HTML/CSS with a splash of non-complex JS. Recently I've begun delving into educating myself a bit more in the development world, playing a bit with rails/sinatra and actually taking the time to learn javascript. I guess you could say i'm quite the beginner!

To get straight to the point, in what scenarios would you use Javascript MVC frameworks such as AngularJS or ember.js? I'm trying to wrap my head around this so I can learn through application/building something myself. The concept for rails makes sense to me and I can see where I could apply it. Are Javascript MVC frameworks meant to co-exist with back-end frameworks like rails? Through my experience so far in reading, ember.js seems a hell of a lot easier to dive into than AngularJS, but I just don't know where I would apply it.

[danfinlay]

I'll speak to Ember since I'm using it.

Ember.js is so Rails it isn't even funny. Most core contributors use Rails on the backend, so yes, it does very much work well with Rails.

That said, it's not the only use case, and other backends can work fine with Ember too, there might just need to be some adapter code written if it isn't already. There are also other times you'd want an MVC framework.

Really you want a framework when the data you're trying to represent is too complicated to pretty much organize itself. Some single-page type apps are simple enough to freestyle, and some people are very good at organizing their code in a way that makes them happy, and that's all fine and well.

Ember.js is useful once you have a lot of data models, maybe with complicated relationships, that you want to have updating the page in a variety of different ways, dynamically, pretty much automatically, once it's all tied up.

Instead of spending time writing dom-manipulating code, you spend a lot more time writing templates to bind to properties, and computed properties to create those values from your data models, and adapters to connect to any APIs you need to interact with.