NodeIterator.previousNode()
  The NodeIterator.previousNode() method returns the
  previous node in the set represented by the NodeIterator and moves the
  position of the iterator backwards within the set.
  This method returns null when the current node is the first node in the
  set.
  In old browsers, as specified in old versions of the specifications, the method may
  throws the INVALID_STATE_ERR DOMException if this method
  is called after the NodeIterator.detach()method. Recent browsers never
  throw.
Syntax
node = nodeIterator.previousNode();
Example
var nodeIterator = document.createNodeIterator(
    document.body,
    NodeFilter.SHOW_ELEMENT,
    { acceptNode: function(node) { return NodeFilter.FILTER_ACCEPT; } },
    false // this optional argument is not used any more
);
currentNode = nodeIterator.nextNode(); // returns the next node
previousNode = nodeIterator.previousNode(); // same result, since we backtracked to the previous node
Specifications
| Specification | 
|---|
| DOM Standard  # dom-nodeiterator-previousnode  | 
Browser compatibility
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See also
- The interface it belongs to: 
NodeIterator.