The node this is a live view of a part of
Only elements which pass this are included (every element by default)
Include every matching descendant (true, like getElementsByTagName), not just the direct element children (false, like Element.children)
How many elements are in the collection right now.
Iterate over the current elements.
The element at the given index, or null when there is none.
The element whose id, or (failing that) whose name attribute, is the given value, or null when there is none.
Simulate the behaviour of the HTMLCollection Class when there is no DOM available: a live view of some of a node's element descendants, recomputed each time it is used rather than kept in sync as they change.