TreeWalker

Instance properties

This interface doesn't inherit any property.

TreeWalker.root Read only

Returns the root Node as specified when the TreeWalker was created.

TreeWalker.whatToShow Read only

Returns an unsigned long which is a bitmask made of constants describing the types of Node that must be presented. Non-matching nodes are skipped, but their children may be included, if relevant.

TreeWalker.filter Read only

Returns the NodeFilter associated with this TreeWalker used to select the relevant nodes.

TreeWalker.currentNode

Is the Node on which the TreeWalker is currently pointing at.

Instance methods

This interface doesn't inherit any method.

TreeWalker.parentNode()

Moves the current Node to the first visible ancestor node in the document order, and returns the found node. It also moves the current node to this one. If no such node exists, or if it is before that the root node defined at the object construction, returns null and the current node is not changed.

TreeWalker.firstChild()

Moves the current Node to the first visible child of the current node, and returns the found child. It also moves the current node to this child. If no such child exists, returns null and the current node is not changed. Note that the node returned by firstChild() is dependent on the value of whatToShow set during instantiation of the TreeWalker object. Assuming the following HTML tree, and if you set the whatToShow to NodeFilter.SHOW_ALL a call to firstChild() will return a Text node and not an HTMLDivElement object.

html

<!doctype html>
<html lang="en">
  <head>
    <title>Demo</title>
  </head>
  <body>
    <div id="container"></div>
  </body>
</html>

js

let walker = document.createTreeWalker(document.body, NodeFilter.SHOW_ALL);
let node = walker.firstChild(); // nodeName: "#text"

But if we do:

js

let walker = document.createTreeWalker(
  document.body,
  NodeFilter.SHOW_ELEMENT,
);
let node = walker.firstChild(); // nodeName: "DIV"

The same applies to nextSibling(), previousSibling(), firstChild() and lastChild()

TreeWalker.lastChild()

Moves the current Node to the last visible child of the current node, and returns the found child. It also moves the current node to this child. If no such child exists, null is returned and the current node is not changed.

TreeWalker.previousSibling()

Moves the current Node to its previous sibling, if any, and returns the found sibling. If there is no such node, return null and the current node is not changed.

TreeWalker.nextSibling()

Moves the current Node to its next sibling, if any, and returns the found sibling. If there is no such node, null is returned and the current node is not changed.

TreeWalker.previousNode()

Moves the current Node to the previous visible node in the document order, and returns the found node. It also moves the current node to this one. If no such node exists, or if it is before that the root node defined at the object construction, returns null and the current node is not changed.

TreeWalker.nextNode()

Moves the current Node to the next visible node in the document order, and returns the found node. It also moves the current node to this one. If no such node exists, returns null and the current node is not changed.

Specifications

Browser compatibility

See also

• The creator method: Document.createTreeWalker().
• Related interface: NodeIterator.