DOM (Document Object Model)

-


What is DOM?
The Document Object Model (DOM) is a cross-platform and language-independent application programming interface that treats a HTML, XHTML, or XML document as a tree structure wherein each node is an object representing a part of the document. The objects can be manipulated programmatically and any visible changes occurring as a result may then be reflected in the display of the document.
The principal standardization of DOM was handled by the World Wide Web Consortium, which last developed a recommendation in 2004. WHATWG took over development of the standard, publishing it as a living document. The W3C now publishes stable snapshots of the WHATWG standard.

History

The history of the Document Object Model is intertwined with the history of the "browser wars" of the late 1990s between Netscape Navigator and Microsoft Internet Explorer, as well as with that of JavaScript and JScript, the first scripting languages to be widely implemented in the layout engines of web browsers.
JavaScript was released by Netscape Communications in 1995 within Netscape Navigator 2.0. Netscape's competitor, Microsoft, released Internet Explorer 3.0 the following year with a reimplementation of JavaScript called JScript. JavaScript and JScript let web developers create web pages with client-side interactivity. The limited facilities for detecting user-generated events and modifying the HTML document in the first generation of these languages eventually became known as "DOM Level 0" or "Legacy DOM." No independent standard was developed for DOM Level 0, but it was partly described in the specifications for HTML 4.
Legacy DOM was limited in the kinds of elements that could be accessed. Form, link and image elements could be referenced with a hierarchical name that began with the root document object. A hierarchical name could make use of either the names or the sequential index of the traversed elements. For example, a form input element could be accessed as either 

  document.formName.inputName or document.forms[0].elements[0].
 
The Legacy DOM enabled client-side form validation and the popular "rollover" effect.
In 1997, Netscape and Microsoft released version 4.0 of Netscape Navigator and Internet Explorer respectively, adding support for Dynamic HTML (DHTML) functionality enabling changes to a loaded HTML document. DHTML required extensions to the rudimentary document object that was available in the Legacy DOM implementations. Although the Legacy DOM implementations were largely compatible since JScript was based on JavaScript, the DHTML DOM extensions were developed in parallel by each browser maker and remained incompatible. These versions of the DOM became known as the "Intermediate DOM."
After the standardization of ECMAScript, the W3C DOM Working Group began drafting a standard DOM specification. The completed specification, known as "DOM Level 1", was recommended by W3C in late 1998. By 2005, large parts of W3C DOM were well-supported by common ECMAScript-enabled browsers, including Microsoft Internet Explorer version 6 (from 2001), Opera, Safari and Gecko-based browsers (like Mozilla, Firefox, SeaMonkey and Camino).

Standards

The W3C DOM Working Group published its final recommendation and subsequently disbanded in 2004. Development efforts migrated to the WHATWG, which continues to maintain a living standard. In 2009, the Web Applications group reorganized DOM activities at the W3C. In 2013, due to a lack of progress and the impending release of HTML5, the DOM Level 4 specification was reassigned to the HTML Working Group to expedite its completion. Meanwhile, in 2015, the Web Applications group was disbanded and DOM stewardship passed to the Web Platform group. Beginning with the publication of DOM Level 4 in 2015, the W3C creates new recommendations based on snapshots of the WHATWG standard.
  • DOM Level 1 provided a complete model for an entire HTML or XML document, including the means to change any portion of the document.
  • 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 3, published in April 2004, added support for XPath and keyboard event handling, as well as an interface for serializing documents as XML.
  • DOM Level 4 was published in 2015. It is a snapshot of the WHATWG living standard.

Applications

Web browsers

To render a document such as an HTML page, most web browsers use an internal model similar to the DOM. The nodes of every document are organized in a tree structure, called the DOM tree, with the topmost node named as "Document object". When an HTML page is rendered in browsers, the browser downloads the HTML into local memory and automatically parses it to display the page on screen.

JavaScript

When a web page is loaded, the browser creates a Document Object Model of the page, which is an object oriented representation of an HTML document, that acts as an interface between JavaScript and the document itself and allows the creation of dynamic web pages:
  • JavaScript can add, change, and remove all of the HTML elements and attributes in the page.
  • JavaScript can change all of the CSS styles in the page.
  • JavaScript can react to all of the existing events in the page.
  • JavaScript can create new events within the page.

Implementations

Because DOM supports navigation in any direction (e.g., parent and previous sibling) and allows for arbitrary modifications, an implementation must at least buffer the document that has been read so far (or some parsed form of it).

Layout engines

Web browsers rely on layout engines to parse HTML into a DOM. Some layout engines, such as Trident/MSHTML, are associated primarily or exclusively with a particular browser, such as Internet Explorer. Others, including Blink, WebKit, and Gecko, are shared by a number of browsers, such as Google Chrome, Opera, Safari, and Firefox. The different layout engines implement the DOM standards to varying degrees of compliance.

Libraries

DOM implementations:
  • libxml2
  • MSXML
  • Xerces is a collection of DOM implementations written in C++, Java and Perl
  • XML for <SCRIPT> is a JavaScript-based DOM implementation
  • PHP.Gt DOM is based on libxml2 and brings DOM level 4 compatibility to the PHP programming language
  • Domino is a Server-side (Node.js) DOM implementation based on Mozilla's dom.js. Domino is used in the MediaWiki stack with Visual Editor.
APIs that expose DOM implementations:
  • JAXP (Java API for XML Processing) is an API for accessing DOM providers
  • Lazarus (Free Pascal IDE) contains two variants of the DOM - with UTF-8 and ANSI format
Inspection tools:
  • DOM Inspector is a web developer tool

Comments

Post a Comment

Popular posts from this blog

Avet – Open Source Anti-Virus Evasion Tool

-
Image
When we want to perform an exploitation to a windows target, we need a payload that is undetectable to Antivirus Solutions. Msfvenom on its own is not enough. So we need an AV evasion tool to make this easy for us. Avet is a tool for building exe files with shellcode payloads for antivirus evasion. Installing Avet First clone the repository to our machine. git clone https://github.com/govolution/avet.git   After that go inside the folder and run the setup file to install wine and other missing components. cd avet/       Run the setup file to install the missing components.   ./setup.sh     Select create  for new installation   Running Avet There are two ways to run avet. Run avet by typing the command below. python avet_fabric.py   There are two ways to run avet. Either by compiling the make_avet script as shown below, or by  running the avet_fabric.py scr...
Read more

PDFCrack - Password Cracking Tool for PDF-files

-
Image
PDFcrack is a GNU/Linux tool for cracking password protected PDF files. It is a very small command line application. It is not preinstalled in kali linux. We can install through command line. For installing pdfcrack open a terminal and enter apt install pdfcrack Syntax and options Usage: pdfcrack -f filename [OPTIONS]           : pdfcrack -f filenmae -w passwordfile.txt OPTIONS : -b, --bench perform benchmark and exit -c, --charset=STRING Use the characters in STRING as charset -w, --wordlist=FILE Use FILE as source of passwords to try -n, --minpw=INTEGER Skip trying passwords shorter than this -m, --maxpw=INTEGER Stop when reaching this passwordlength -l, --loadState=FILE Continue from the state saved in FILENAME -o, --owner Work with the ownerpassword -u, --user Work with the userpassword (default) -p, --password=STRING Give userpassword to speed up breaking ownerpassword (...
Read more

How to Repair Kali Linux grub after installing Windows in Dual boot System

-
Image
If your System has primary OS Windows then you install your secondary OS Kali Linux. That will be OK, Kali Linux puts boot entry of Windows automatically for you. At initial boot menu you can see both OS entry to boot. If your windows is corrupt in dual boot system or if you want to install windows as secondary OS after installing Kali Linux as primary OS. You may face corrupt boot-loader menu. You wont be able to boot Kali Linux any more because Windows wont put entry of Kali Linux automatically in their boot menu. So this post motive is to help those guys which are facing those problems subjecting to corrupt Boot-loader. There are mainly two methods: 1. Repair Grub via Kali Linux live USB. 2. Repair Grub Via Boot-rapair-disk. Method 1# Repair Grub via Kali Linux live USB It is up to you which you want to choose but if you are Linux familiar then go for this method. Requirements 1. A Kali Linux ISO image. You can download here: Download Kali Linux...
Read more