Document Object Model

Describing the specification differences and browser supports among DOM Level 1, Level 2and Level 3. DOM Level 1 was published in 1998 as a single W3C recommendation, consisting of two modules, the Core and the HTML module. DOM Level 2 was published in late 2000. It introduced the “getElementById” function as well as an event model and support for XML namespaces and CSS. DOM Level 2 consists of several W3C recommendations, published between 2000 and 2003, and has several modules, some of them being Core, HTML, these two improving and refining what was done in Level 1, and additional modules Events, Traversal-Range, Views, and Style.

The main difference between DOM Level 1 Core and DOM Level 2 Core is that Level 2 Core is suitable for scripting XML with namespaces by having namespace aware methods and properties which are not available in Level 1 Core. The main difference between DOM Level 1 HTML and DOM Level 2 HTML is that Level 2 HTML is closer to the features in existing user agents. Also, at least in theory DOM Level 2 HTML applies to both HTML 4.01 as well as XHTML 1.0 documents while DOM Level 1 HTML applies only to HTML 4.01 documents.

DOM Level 3, the current release of the DOM specification, published in April 2004, added support for XPath and keyboard event handling, as well as an interface for serializing documents as XML. Since the beginning of 2004 there are also W3C DOM Level 3 recommendations for Core, Load and Save, and Validation where Level 3 Core again improves and refines Level 2 Core while the other two modules add new features.

Table of five differences of DOM Level 3, Level 2, and Level 1

Differences

DOM Level 1
DOM Level 2
DOM Level 3

Core Module
The goal of the DOM specification is to define a programmatic interface for XML and HTML. The DOM Level 1 specification is separated into two parts: Core and HTML The DOM Level 2 Core is made of a set of core interfaces to create and manipulate the structure and contents of a document. This version enhances DOM Level 2 Core by completing the mapping between DOM and the XML Information Set [XML Information Set],

HTML Module

This specification defines the Document Object Model Level 2 HTML, a platform- and language-neutral interface that allows programs and scripts to dynamically access and update the content and structure of [HTML 4.01] and [XHTML 1.0] documents

Style Module

This specification defines the Document Object Model Level 2 Style Sheets and Cascading Style Sheets (CSS), a platform- and language-neutral interface that allows programs and scripts to dynamically access and update the content and of style sheets documents.

Traversal-Range

This specification defines the Document Object Model Level 2 Traversal and Range, platform- and language-neutral interfaces that allow programs and scripts to dynamically traverse and identify a range of content in a document

Views Module

This specification defines the Document Object Model Level 2 Views, a platform- and language-neutral interface that allows programs and scripts to dynamically access and update the content of a representation of a document.

Load and Save Module

This document contains the Document Object Model Level 3 Load and Save specification and is a W3C Recommendation

Validation

This module provides the guidance to programs and scripts to dynamically update the content and the structure of documents while ensuring that the document remains valid, or to ensure that the document becomes valid.