Dom node vs element, what is the difference between the two?
Document Object Model (DOM) is an interface that treats HTML or XML documents as a tree structure, in which each Each node is an object of the document. DOM also provides a set of methods to query the tree, change structure, and style.
DOM also uses the term element (Element) which is very similar to a node. So, what is the difference between DOM nodes and elements?
1. DOM nodes
The key to understanding the difference between nodes and elements is to understand what a node is.
From a higher perspective, a DOM document consists of a node hierarchy. Each node can have parents and/or children.
Look at the following HTML document:
<!DOCTYPE html>
<html>
<head>
<title>My Page</title>
</head>
<body>
<!-- Page Body -->
<h2 id="My-nbsp-Page">My Page</h2>
<p id="content">Thank you for visiting my web page!</p>
</body>
</html>The document contains the following node hierarchy:
## is a node in the document tree. It has 2 child nodes:
and .
A node with 3 child nodes: Comment node , Title, paragraph . The parent node of the
node is the node. The tag in the HTML document represents a node. Interestingly, ordinary text is also a node. Paragraph node
has 1 child node: text node "Thank you for visiting my web page!".
1.2 Node Type
How do we distinguish these different types of nodes? The answer lies in the DOM Node interface, specifically theNode.nodeType attribute.
Node.nodeType can have one of the following values representing the node type:
- Node.ELEMENT_NODE
- Node.ATTRIBUTE_NODE
- Node.TEXT_NODE
- Node.CDATA_SECTION_NODE
- Node.PROCESSING_INSTRUCTION_NODE
- Node.COMMENT_NODE
- Node.DOCUMENT_NODE
- Node. DOCUMENT_TYPE_NODE
- Node.DOCUMENT_FRAGMENT_NODE
- Node.NOTATION_NODE
Node.ELEMENT_NODE represents element nodes, Node.TEXT_NODE represents the text node, Node.DOCUMENT_NODE the document node, and so on.
nodeType attribute:
const paragraph = document.querySelector('p'); paragraph.nodeType === Node.ELEMENT_NODE; // => trueThe node type that represents the entire node document tree is
Node.DOCUMENT_NODE：
document.nodeType === Node.DOCUMENT_NODE; // => true
2. DOM elements
After mastering the knowledge of DOM nodes, it is now time to distinguish between DOM nodes and elements. If you understand node terminology, the answer is obvious: elements are nodes of a specific typeelement (Node.ELEMENT_NODE), as well as types such as document, comment, text, etc.
,
, , ,
are all elements because they are represented by tags.
Node is the constructor of the node, HTMLElement is Constructor for elements in JS DOM. A paragraph is both a node and an element, it is an instance of both Node and HTMLElement
const paragraph = document.querySelector('p'); paragraph instanceof Node; // => true paragraph instanceof HTMLElement; // => trueSimply put, elements are subtypes of nodes, just like cats are animals The subtypes are the same.
3. DOM attributes: nodes and elements
In addition to distinguishing between nodes and elements, it is also necessary to distinguish between DOM attributes that contain only nodes or only elements. The following properties of the node type evaluate to a node or collection of nodes (NodeList):
node.parentNode; // Node or null node.firstChild; // Node or null node.lastChild; // Node or null node.childNodes; // NodeListHowever, the following properties evaluate to an element or collection of elements (
HTMLCollection):
node.parentElement; // HTMLElement or null node.children; // HTMLCollectionSince both
node.childNodes and node.children return a list of children, why do you have both properties? good question!
<p> <b>Thank you</b> for visiting my web page! </p>Open the
demo and look at the childNodes and children# of the paragraph node ##Properties: <pre class='brush:php;toolbar:false;'>const paragraph = document.querySelector(&#39;p&#39;);
paragraph.childNodes; // NodeList: [HTMLElement, Text]
paragraph.children; // HTMLCollection: [HTMLElement]</pre>
The collection contains 2 nodes: <b>Thank you</b>, and for visiting my web page!Text node! However, the
collection contains only 1 item: <b>Thank you</b>. Since
only contains elements, the text node is not included here because its type is text (Node.TEXT_NODE), not element (Node.ELEMENT_NODE). <p>Having both <code>node.childNodes and node.children, we can choose the set of children to access: all child nodes or only children that are elements.
4. Summary
A DOM document is a hierarchical collection of nodes, each node can have parents and/or children. Understanding the difference between DOM nodes and elements is easy if you understand what nodes are.
Nodes have types, and element types are one of them. Elements are represented by tags in HTML documents.
English original address: https://dmitripautin.com/dom-node-element/
Author: Shadeed
Source: dmitripavlutin
For more programming-related knowledge, please visit: Programming Teaching! !
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