Document.createTreeWalker()

Document.createTreeWalker() 方法，能建立一個 TreeWalker 物件並傳回.

語法

treeWalker = document.createTreeWalker(root, whatToShow, filter, entityReferenceExpansion);

參數

root

是這個 TreeWalker 遍歷的根節點(root Node). Typically this will be an element owned by the document.

whatToShow 選擇性

Is an optional unsigned long representing a bitmask created by combining the constant properties of NodeFilter. 它是一種方便的方法，用來過濾某些類型的節點。 It defaults to 0xFFFFFFFF representing the SHOW_ALL constant.

Constant	數值	說明
NodeFilter.SHOW_ALL	-1 (that is the max value of unsigned long)	顯示所有節點.
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	顯示文字節點(Text nodes).

filter 選擇性

是一個可選的 NodeFilter, 這是一個物件有著 acceptNode 方法, 這方法被 TreeWalker 呼叫來決定是否接受通過 whatToShow 檢查的節點.

entityReferenceExpansion 選擇性

Is a Boolean flag indicating if when discarding an EntityReference its whole sub-tree must be discarded at the same time.

Example

The following example goes through all nodes in the body, reduces the set of nodes to elements, simply 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 = [];

while(treeWalker.nextNode()) nodeList.push(treeWalker.currentNode);

Specifications

Browser compatibility

See also

• The interface of the object it creates: TreeWalker.
• createTreeWalker on MSDN