Document.createTreeWalker()

The Document.createTreeWalker() creator method returns a newly created TreeWalker object.

Syntax

document.createTreeWalker(root[, whatToShow[, filter[, expandEntityReferences]]]);

Parameters

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 -1 (that is the max value of unsigned long) Shows all nodes.
NodeFilter.SHOW_ATTRIBUTE 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 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 32 Shows Entity nodes. This is meaningful only when creating a TreeWalker with an Entity node as its root; in this case, it means that the Entity node will appear in the first position of the traversal. Since entities are not part of the document tree, they do not appear when traversing over the document tree.
NodeFilter.SHOW_ENTITY_REFERENCE 16 Shows EntityReference nodes.
NodeFilter.SHOW_NOTATION 2048 Shows Notation nodes. This is meaningful only when creating a TreeWalker with a Notation node as its root; in this case, it means that the Notation node will appear in the first position of the traversal. Since entities are not part of the document tree, they do not appear when traversing over the document tree.
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.
expandEntityReferences Optional
A Boolean flag indicating if when discarding an EntityReference its whole sub-tree must be discarded at the same time.

Return value

A new TreeWalker object.

Example

The following example goes through all nodes in the body, reduces the set of nodes to elements, passes through as acceptable each node (it could reduce the set in the acceptNode() method instead), 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.

var treeWalker = document.createTreeWalker(
  document.body,
  NodeFilter.SHOW_ELEMENT,
  { acceptNode: function(node) { return NodeFilter.FILTER_ACCEPT; } },
  false
);

var nodeList = [];
var currentNode = treeWalker.currentNode;

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

Specifications

Specification
DOM Standard (DOM)
# dom-document-createtreewalker

Browser compatibility

BCD tables only load in the browser

See also

  • The interface of the object it creates: TreeWalker.