Check whether string of brackets are well-formed
There are some issues with the code:


isBracketBalanced - Should be plural. It checks more than one bracket.
bracketIsBalanced - Is basically the same name as the parent function, except it does more than just check if the bracket is balanced. It also manipulates the stack. 
braces - Didn't we just call them brackets?
expectCloseStack declaration - This is perhaps just my personal preference, but to me, writing the declaration after a comma like that makes me look twice to see if it is part of the object that was declared above it.


All in all, I find this solution a bit harder to read than the original. Also, it's actually not more concise.