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TreeWalker

files/en-us/web/api/treewalker/index.md

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{{ APIRef("DOM") }}

The TreeWalker object represents the nodes of a document subtree and a position within them.

A TreeWalker can be created using the {{domxref("Document.createTreeWalker()")}} method.

Instance properties

This interface doesn't inherit any property.

  • {{domxref("TreeWalker.root")}} {{ReadOnlyInline}}
    • : Returns the root {{domxref("Node")}} as specified when the TreeWalker was created.
  • {{domxref("TreeWalker.whatToShow")}} {{ReadOnlyInline}}
    • : Returns an unsigned long which is a bitmask made of constants describing the types of {{domxref("Node")}} that must be presented. Non-matching nodes are skipped, but their children may be included, if relevant.
  • {{domxref("TreeWalker.filter")}} {{ReadOnlyInline}}
    • : Returns the NodeFilter associated with this TreeWalker used to select the relevant nodes.
  • {{domxref("TreeWalker.currentNode")}}
    • : Is the {{domxref("Node")}} on which the TreeWalker is currently pointing at.

Instance methods

This interface doesn't inherit any method.

[!NOTE] In the context of a TreeWalker, a node is visible if it exists in the logical view determined by the whatToShow and filter parameter arguments. (Whether or not the node is visible on the screen is irrelevant.)

  • {{domxref("TreeWalker.parentNode()")}}

    • : Moves the current {{domxref("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.

  • {{domxref("TreeWalker.firstChild()")}}

    • : Moves the current {{domxref("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()

  • {{domxref("TreeWalker.lastChild()")}}

    • : Moves the current {{domxref("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.

  • {{domxref("TreeWalker.previousSibling()")}}

    • : Moves the current {{domxref("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.

  • {{domxref("TreeWalker.nextSibling()")}}

    • : Moves the current {{domxref("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.

  • {{domxref("TreeWalker.previousNode()")}}

    • : Moves the current {{domxref("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.

  • {{domxref("TreeWalker.nextNode()")}}

    • : Moves the current {{domxref("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

{{Specifications}}

Browser compatibility

{{Compat}}

See also

  • The creator method: {{domxref("Document.createTreeWalker()")}}.
  • Related interface: {{domxref("NodeIterator")}}.