Angular JS: Common Pitfalls using scopes

http://thenittygritty.co/angularjs-pitfalls-using-scopes

Any amount of changes must be applied by calling $apply to invoke the digest cycle. However, you don't have to if it's not required.
Sometimes it might not be suited to apply the digest cycle after every single change since it could massively decrease performance.

https://www.airpair.com/angularjs/posts/top-10-mistakes-angularjs-developers-make

http://www.thinkingmedia.ca/2015/01/learn-how-to-use-scopes-properly-in-angularjs/