Shopify/batman — pull request #598 by mattwdh (2012-12-03 18:54:49+00:00)
Title: Faster Iteration

+ Replace the `_eachSourceChangeEvent` helper functions with the plain code.
+ Replace the `forEach` in these new pieces of code with `for-in`
+ Replace the `forEach` in `Property#eachObserver` with `for-in`
+ Replace `forEach` on the `SimpleSet` with `for-in`

Working through this I noticed that `Property#eachObserver` calls `slice` in order to be safe. This is a super super hot function so we should try and remove the `slice` if possible. Kristian, I think this falls into your hands?

@nciagra @kristianpd