How does ng-repeat work?

Question

I dissected ng-repeat and extracted the code blocks attached, seeing that these comprise the logic that handles the repeating algorithm (which I want to und

Answer 1

After some tinkering with the directive, I became familiar with ng-repeaters code, and managed to answer some of my questions. I highlighted in bold the things I couldn't yet figure out on my own, and would appreciate if anyone could shed some light on the bold parts:

1. The ID is tested for hasOwnProperty, because they use that method to check whether the ID is present in the iteration objects (lastBlockMap, nextBlockMap) (this process explained below). I couldn't find out on what scenario this can actually happen, however.
2. I was correct in my assumption. nextBlockMap contains all items that will be transcluded on the current model change. lastBlockMap contains everything from the previous model update. It used for finding duplicates in the collection.
3. OK, this one is pretty straightforward actually. In this for loop, ng-repeat fills up nextBlockMap with items from lastBlockMap. Looking at the order of ifs, it's easy to see that if the item cannot be found in lastBlockMap, but it is already present in nextBlockMap (meaning, it was already copied there from lastBlockMap, and therefore its trackById appears twice in the collection) - it's a duplicate. What the forEach does is simply run through all initialized items in nextBlockMap (blocks that have a startNode property) and push their ID back into lastBlockMap. I cannot however understand why this is necessary.
4. The only reason I could find for separating nextBlockOrder (all trackByIds in an array) from nextBlockMap (all block objects in a trackById hash), is this line, which working with an array makes it an easy and simple operation: if (nextBlockOrder[index - 1]) previousNode = nextBlockOrder[index - 1].endNode;. It is explained in the answers to question 5 and 6:
5. block.startNode and block.endNode are the first and last DOM nodes in the block belonging to an item in the collected being repeated. Therefore, this line here sets previousNode to reference the last DOM node of the previous item in the repeater.
6. previousNode is then used as the first node, in a loop that checks how the DOM changed when items have been moved around or removed from the repeater collection - again, only in case we are not working with the first block in the array.
7. This is easy - it initializes the block - assigning the $scope and startNode and endNode for later reference, and saves everything in nextBlockMap. The comment created right after the cloned element, is there to guarantee we always have an endNode.