Node - Web APIs 编辑

The DOM Node interface is an abstract base class upon which many other DOM API objects are based, thus letting those object types to be used similarly and often interchangeably. As an abstract class, there is no such thing as a plain Node object. All objects that implement Node functionality are based on one of its subclasses. Most notable are Document, Element, and DocumentFragment.

In addition, every kind of DOM node is represented by an interface based on Node. These include Attr, CharacterData (which Text, Comment, and CDATASection are all based on), ProcessingInstruction, DocumentType, Notation, Entity, and EntityReference.

In some cases, a particular feature of the base Node interface may not apply to one of its child interfaces; in that case, the inheriting node may return null or throw an exception, depending on circumstances. For example, attempting to add children to a node type that cannot have children will throw an exception.

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Properties

In addition to the properties below, Node inherits properties from its parent, EventTarget.

Node.baseURIRead only

Returns a DOMString representing the base URL of the document containing the Node.

Node.childNodesRead only

Returns a live NodeList containing all the children of this node (including elements, text and comments). NodeList being live means that if the children of the Node change, the NodeList object is automatically updated.

Node.firstChildRead only

Returns a Node representing the first direct child node of the node, or null if the node has no child.

Node.isConnectedRead only

A boolean indicating whether or not the Node is connected (directly or indirectly) to the context object, e.g. the Document object in the case of the normal DOM, or the ShadowRoot in the case of a shadow DOM.

Node.lastChildRead only

Returns a Node representing the last direct child node of the node, or null if the node has no child.

Node.nextSiblingRead only

Returns a Node representing the next node in the tree, or null if there isn't such node.

Node.nodeNameRead only

Returns a DOMString containing the name of the Node. The structure of the name will differ with the node type. E.g. An HTMLElement will contain the name of the corresponding tag, like 'audio' for an HTMLAudioElement, a Text node will have the '#text' string, or a Document node will have the '#document' string.

Node.nodeTypeRead only

Returns an unsigned short representing the type of the node. Possible values are:

Name	Value
ELEMENT_NODE	1
ATTRIBUTE_NODE	2
TEXT_NODE	3
CDATA_SECTION_NODE	4
ENTITY_REFERENCE_NODE	5
ENTITY_NODE	6
PROCESSING_INSTRUCTION_NODE	7
COMMENT_NODE	8
DOCUMENT_NODE	9
DOCUMENT_TYPE_NODE	10
DOCUMENT_FRAGMENT_NODE	11
NOTATION_NODE	12

Node.nodeValue

Returns / Sets the value of the current node.

Node.ownerDocumentRead only

Returns the Document that this node belongs to. If the node is itself a document, returns null.

Node.parentNodeRead only

Returns a Node that is the parent of this node. If there is no such node, like if this node is the top of the tree or if doesn't participate in a tree, this property returns null.

Node.parentElementRead only

Returns an Element that is the parent of this node. If the node has no parent, or if that parent is not an Element, this property returns null.

Node.previousSiblingRead only

Returns a Node representing the previous node in the tree, or null if there isn't such node.

Node.textContent

Returns / Sets the textual content of an element and all its descendants.

Obsolete properties

Node.localName Read only

Returns a DOMString representing the local part of the qualified name of an element.

Note: In Firefox 3.5 and earlier, the property upper-cases the local name for HTML elements (but not XHTML elements). In later versions, this does not happen, so the property is in lower case for both HTML and XHTML.

Node.namespaceURI Read only

The namespace URI of this node, or null if it is no namespace.

Note: In Firefox 3.5 and earlier, HTML elements are in no namespace. In later versions, HTML elements are in the http://www.w3.org/1999/xhtml/ namespace in both HTML and XML trees.

Node.prefix Read only

Is a DOMString representing the namespace prefix of the node, or null if no prefix is specified.

Methods

In addition to the properties below, Node inherits methods from its parent, EventTarget.

Node.appendChild(childNode)

Adds the specified childNode argument as the last child to the current node.
If the argument referenced an existing node on the DOM tree, the node will be detached from its current position and attached at the new position.

Node.cloneNode()

Clone a Node, and optionally, all of its contents. By default, it clones the content of the node.

Node.compareDocumentPosition()

Compares the position of the current node against another node in any other document.

Node.contains()

Returns a Boolean value indicating whether or not a node is a descendant of the calling node.

Node.getBoxQuads()

Returns a list of the node's CSS boxes relative to another node.

Node.getRootNode()

Returns the context object's root which optionally includes the shadow root if it is available. 

Node.hasChildNodes()

Returns a Boolean indicating whether or not the element has any child nodes.

Node.insertBefore()

Inserts a Node before the reference node as a child of a specified parent node.

Node.isDefaultNamespace()

Accepts a namespace URI as an argument and returns a Boolean with a value of true if the namespace is the default namespace on the given node or false if not.

Node.isEqualNode()

Returns a Boolean which indicates whether or not two nodes are of the same type and all their defining data points match.

Node.isSameNode()

Returns a Boolean value indicating whether or not the two nodes are the same (that is, they reference the same object).

Node.lookupPrefix()

Returns a DOMString containing the prefix for a given namespace URI, if present, and null if not. When multiple prefixes are possible, the result is implementation-dependent.

Node.lookupNamespaceURI()

Accepts a prefix and returns the namespace URI associated with it on the given node if found (and null if not). Supplying null for the prefix will return the default namespace.

Node.normalize()

Clean up all the text nodes under this element (merge adjacent, remove empty).

Node.removeChild()

Removes a child node from the current element, which must be a child of the current node.

Node.replaceChild()

Replaces one child Node of the current one with the second one given in parameter.

Obsolete methods

Node.getUserData() 

Allows a user to get some DOMUserData from the node.

Node.hasAttributes() 

Returns a Boolean indicating if the element has any attributes, or not.

Node.isSupported() 

Returns a Boolean flag containing the result of a test whether the DOM implementation implements a specific feature and this feature is supported by the specific node.

Node.setUserData() 

Allows a user to attach, or remove, DOMUserData to the node.

Examples

Remove all children nested within a node

function removeAllChildren(element) {
  while (element.firstChild) {
    element.removeChild(element.firstChild)
  }
}

Sample usage

/* Note: or use document.body.textContent = "" */
removeAllChildren(document.body)

Recurse through child nodes

The following function recursively calls a callback function for each node contained by a root node (including the root itself):

function eachNode(rootNode, callback) {
	if (!callback) {
		const nodes = []
		eachNode(rootNode, function(node) {
			nodes.push(node)
		})
		return nodes
	}

	if (false === callback(rootNode)) {
		return false
    }

	if (rootNode.hasChildNodes()) {
		const nodes = rootNode.childNodes
		for (let i = 0, l = nodes.length; i < l; ++i) {
			if (false === eachNode(nodes[i], callback)) {
				return
            }
        }
	}
}

Syntax

eachNode(rootNode, callback)

Description

Recursively calls a function for each descendant node of rootNode (including the root itself).

If callback is omitted, the function returns an Array instead, which contains rootNode and all nodes contained within.

If callback is provided, and it returns Boolean false when called, the current recursion level is aborted, and the function resumes execution at the last parent's level. This can be used to abort loops once a node has been found (such as searching for a text node which contains a certain string).

Parameters

rootNode

The Node object whose descendants will be recursed through.

callback Optional

An optional callback function that receives a Node as its only argument. If omitted, eachNode returns an Array of every node contained within rootNode (including the root itself).

Sample usage

The following example prints the textContent properties of each <span> tag in a <div> element named "box":

<div id="box">
  <span>Foo</span>
  <span>Bar</span>
  <span>Baz</span>
</div>

const box = document.getElementById("box")
eachNode(box, function(node) {
  if (null != node.textContent) {
    console.log(node.textContent)
  }
})

The above will result in the following strings printing to the user's console:

"\n\t", "Foo", "\n\t", "Bar", "\n\t", "Baz"

Note: Whitespace forms part of a Text node, meaning indentation and newlines form separate Text between the Element nodes.

Realistic usage

The following demonstrates a real-world use of the eachNode() function: searching for text on a web-page.

We use a wrapper function named grep to do the searching:

function grep(parentNode, pattern) {
	const matches = []
	let endScan = false

	eachNode(parentNode, function(node){
		if (endScan) {
			return false
        }

		// Ignore anything which isn't a text node
		if (node.nodeType !== Node.TEXT_NODE) {
			return
        }

		if (typeof pattern === "string") {
			if (-1 !== node.textContent.indexOf(pattern)) {
				matches.push(node)
            }
		}
		else if (pattern.test(node.textContent)) {
			if (!pattern.global) {
				endScan = true
				matches = node
			}
			else {
                matches.push(node)
            }
		}
	})

	return matches
}

For example, to find Text nodes that contain typos:

const typos = ["teh", "adn", "btu", "adress", "youre", "msitakes"]
const pattern = new RegExp("\\b(" + typos.join("|") + ")\\b", "gi")
const mistakes = grep(document.body, pattern)
console.log(mistakes)

Specifications

Browser compatibility

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