Iterators are used to step through a set of nodes, e.g. the set of nodes in a NodeList, the document subtree governed by a particular Node, the results of a query, or any other set of nodes. The set of nodes to be iterated is determined by the implementation of
the NodeIterator. DOM Level 2 specifies a single NodeIterator implementation for document-order traversal of a document subtree. Instances of these iterators are created by calling DocumentTraversal.createNodeIterator().