Shulou(Shulou.com)06/02 Report--

What are the four basic interfaces of the DOM object model? aiming at this problem, this article introduces the corresponding analysis and solution in detail, hoping to help more partners who want to solve this problem to find a more simple and feasible method.

In the DOM object model interface specification, there are four basic interfaces. Among these four basic interfaces, the Document interface is the entry point for manipulating documents, which is inherited from the Node interface. The Node interface is the parent of most other interfaces, while the NodeList interface is a collection of nodes that contains all the child nodes in a node. The NamedNodeMap interface is also a collection of nodes.

Four basic interfaces of DOM object model

In the DOM object model interface specification, there are four basic interfaces: Document,Node,NodeList and NamedNodeMap. Of these four basic interfaces, the Document interface is the entry point for manipulating documents, which is inherited from the Node interface. The Node interface is the parent of most other interfaces, and interfaces such as Documet,Element,Attribute,Text,Comment inherit from the Node interface. The NodeList interface is a collection of nodes that contains all the children of a node. NamedNodeMap interface is also a collection of nodes. Through this interface, we can establish an one-to-one mapping relationship between node names and nodes, so that node names can be used to access specific nodes directly. The following is a brief introduction to each of these four interfaces.

1.Document interface

The Document interface represents the entire XML/HTML document, so it is the root of the entire document tree, providing an entrance to access and manipulate the data in the document.

Because elements, text nodes, comments, processing instructions and so on can not exist independently from the context of the document, the Document interface provides a method to create other node objects. All node objects created by this method have an ownerDocument attribute, which is used to indicate who created the current node and the relationship between the node and Document.

In the DOM tree, the relationship between the Document interface and other interfaces is shown in the following figure:

As can be seen from the figure, the Document node is the root node in the DOM tree, that is, the entry node that operates on the XML document. Through the Docuemt node, you can access other nodes in the document, such as processing instructions, comments, document types, the root element node of the XML document, and so on. In addition, we can also see from the above figure that in a DOM tree, a Document node can contain multiple processing instructions and multiple comments as its child nodes, while both the document type node and the XML document root element node are *.

A detailed description of the IDL (InterfaceDefinitionLanguage Interface definition language) definition of the Document interface and some of the more commonly used properties and methods can be found in many reference books.

2.Node interface

Node interface plays an important role in the whole DOM tree. A large part of DOM object model interface inherits from Node interface, for example, Element, Attr, CDATASection and other interfaces are inherited from Node. In the DOM tree, the Node interface represents a node in the tree. A typical Node interface is shown in the following figure:

As shown in the figure, the Node interface provides access to the content and information of elements in the DOM tree, and provides support for traversing elements in the DOM tree.

3.NodeList interface

The NodeList interface provides an abstract definition of a node set, and it does not contain a definition of how to implement this node set. NodeList is used to represent a group of nodes that have a sequential relationship, such as a sequence of child nodes of a node. In addition, it appears in the return values of some methods, such as GetNodeByName.

In the DOM object model, the NodeList object is "live", in other words, changes to the document are directly reflected in the relevant NodeList object. For example, if you get a NodeList object through DOM that contains a collection of all the children of an Element node, then when you operate on the Element node through DOM (add, delete, change the children in the node), these changes will be automatically reflected in the NodeList object without the need for the DOM object model application to do anything else.

Each item in NodeList can be accessed through an index with a value starting at 0.

4.NamedNodeMap interface

Objects that implement the NamedNodeMap interface contain a collection of nodes that can be accessed by name. Note, however, that NamedNodeMap does not inherit from NodeList, and the nodes in the node set it contains are unordered. Although these nodes can also be accessed by index, this only provides a simple way to enumerate the nodes contained in NamedNodeMap, and does not mean that there is an order for nodes in NamedNodeMap in the DOM object model specification.

NamedNodeMap represents the one-to-one correspondence between a set of nodes and their names, and this interface is mainly used in the representation of attribute nodes.

Like NodeList, the NamedNodeMap object is "live" in DOM.

This is the answer to the question about what are the four basic interfaces of the DOM object model. I hope the above content can be of some help to you. If you still have a lot of doubts to be solved, you can follow the industry information channel for more related knowledge.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.