DOM means Document object model. The DOM is a programming language interface for HTML and XML(Extensible markup language) documents. It defines the logical structure of documents and the way a document is accessed and manipulated.
DOM is a way to represent the web page in the structured hierarchical way so that it will become easier for programmers and users to glide through the document.
Structure of DOM:
DOM can be thought of as Tree or forest (which is more than one tree). The term structure model is sometimes used to describe the tree-like representation of a document. One important property of DOM structure models is structural isomorphism.
Why is it called Object Model?
Documents are modeled using objects, and the model includes not only the structure of a document but also the behavior of a document and the objects of which it is composed of like tag elements with attributes in HTML.
Accessing the DOM
Levels of DOM:
Level 0: Provides a low-level set of interfaces.
Level 1: DOM level 1 can be described in two parts: CORE and HTML.
CORE provides low-level interfaces that can be used to represent any structured document.
HTML provides high-level interfaces that can be used to represent HTML documents.
Level 2 : consists of six specifications: CORE2, VIEWS, EVENTS, STYLE, TRAVERSAL, and RANGE.
CORE2: extends the functionality of CORE specified by DOM level 1.
VIEWS: views allows programs to dynamically access and manipulate the content of the document.
EVENTS: Events are scripts that are either executed by the browser when the user reacts to the web page.
STYLE: allows programs to dynamically access and manipulate the content of style sheets.
TRAVERSAL: allows programs to dynamically traverse the document.
RANGE: allows programs to dynamically identify a range of content in the document.
Level 3: consists of five different specifications: CORE3, LOAD and SAVE, VALIDATION, EVENTS, and XPATH.
CORE3: extends the functionality of CORE specified by DOM level 2.
LOAD and SAVE: allows the program to dynamically load the content of the XML document into the
DOM document and save the DOM Document into an XML document by serialization.
VALIDATION: allows the program to dynamically update the content and structure of the document while ensuring the document remains valid.
EVENTS: extends the functionality of Events specified by DOM Level 2.
XPATH: XPATH is a path language that can be used to access the DOM tree.