Document.createTreeWalker()

root

A root Node of this TreeWalker traversal. Typically this will be an element owned by the document.

whatToShow Optional

A unsigned long representing a bitmask created by combining the constant properties of NodeFilter. It is a convenient way of filtering for certain types of node. It defaults to 0xFFFFFFFF representing the SHOW_ALL constant.

Constant	Numerical value	Description
NodeFilter.SHOW_ALL	4294967295 (that is the max value of unsigned long)	Shows all nodes.
NodeFilter.SHOW_ATTRIBUTE Deprecated	2	Shows attribute Attr nodes. This is meaningful only when creating a TreeWalker with an Attr node as its root; in this case, it means that the attribute node will appear in the first position of the iteration or traversal. Since attributes are never children of other nodes, they do not appear when traversing over the document tree.
NodeFilter.SHOW_CDATA_SECTION Deprecated	8	Shows CDATASection nodes.
NodeFilter.SHOW_COMMENT	128	Shows Comment nodes.
NodeFilter.SHOW_DOCUMENT	256	Shows Document nodes.
NodeFilter.SHOW_DOCUMENT_FRAGMENT	1024	Shows DocumentFragment nodes.
NodeFilter.SHOW_DOCUMENT_TYPE	512	Shows DocumentType nodes.
NodeFilter.SHOW_ELEMENT	1	Shows Element nodes.
NodeFilter.SHOW_ENTITY Deprecated	32	Legacy, no longer usable.
NodeFilter.SHOW_ENTITY_REFERENCE Deprecated	16	Legacy, no longer usable.
NodeFilter.SHOW_NOTATION Deprecated	2048	Legacy, no longer usable.
NodeFilter.SHOW_PROCESSING_INSTRUCTION	64	Shows ProcessingInstruction nodes.
NodeFilter.SHOW_TEXT	4	Shows Text nodes.

filter Optional

A NodeFilter, that is an object with a method acceptNode, which is called by the TreeWalker to determine whether or not to accept a node that has passed the whatToShow check.

A new TreeWalker object.

The following example goes through all nodes in the body, filters out any non nodes that aren't elements (with the NodeFilter.SHOW_ELEMENT value), marks each remaining node as acceptable (The acceptNode() method could make a different decision.), and then makes use of tree walker iterator that is created to advance through the nodes (now all elements) and push them into an array.

const treeWalker = document.createTreeWalker(
  document.body,
  NodeFilter.SHOW_ELEMENT,
  {
    acceptNode(node) {
      return NodeFilter.FILTER_ACCEPT;
    },
  }
);

const nodeList = [];
let currentNode = treeWalker.currentNode;

while (currentNode) {
  nodeList.push(currentNode);
  currentNode = treeWalker.nextNode();
}

• The interface of the object it creates: TreeWalker.