Angular
Very flexible, we can do whatever we want, in whatever way.

Ember
It is hard to write ugly code cuz we need to follow the rules. Good for teamwork.

Backbone
Two-way data-binding is not free.
It will just do what we tell it to do. Thus, we need to write a lot of code.

React
It is V in MVC.
Two-way data-binding is not free.
Update is very cheap by doming DOM diff & update.
Easy & great cross-platform including mobile phone apps.
JSX which, like CoffeeScript, transpiles into native JavaScript.

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