NodeIterator: previousNode() method

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.

previousNode()

const nodeIterator = document.createNodeIterator(
  document.body,
  NodeFilter.SHOW_ELEMENT,
  {
    acceptNode(node) {
      return NodeFilter.FILTER_ACCEPT;
    },
  },
);
currentNode = nodeIterator.nextNode(); // returns the next node
previousNode = nodeIterator.previousNode(); // same result, since we backtracked to the previous node