-------> Start marking on the page <-------
-------> Find the markerPen Controls at the bottom <-------
(Sample Data taken from wikipedia on jQuery article)
jQuery is a cross-platform JavaScript library designed to simplify the client-side scripting of HTML. jQuery is the most popular JavaScript library in use today, with installation on 65% of the top 10 million highest-trafficked sites on the Web. jQuery is free, open-source software licensed under the MIT License.
jQuery's syntax is designed to make it easier to navigate a document, select DOM elements, create animations, handle events, and develop Ajax applications. jQuery also provides capabilities for developers to create plug-ins on top of the JavaScript library. This enables developers to create abstractions for low-level interaction and animation, advanced effects and high-level, themeable widgets. The modular approach to the jQuery library allows the creation of powerful dynamic web pages and Web applications.
The set of jQuery core features—DOM element selections, traversal and manipulation—enabled by its selector engine (named "Sizzle" from v1.3), created a new "programming style", fusing algorithms and DOM data structures. This style influenced the architecture of other JavaScript frameworks like YUI v3 and Dojo, later stimulating the creation of the standard Selectors API.
Microsoft and Nokia bundle jQuery on their platforms. Microsoft includes it with Visual Studio for use within Microsoft's ASP.NET AJAX and ASP.NET MVC frameworks while Nokia has integrated it into the Web Run-Time widget development platform. jQuery has also been used in MediaWiki since version 1.16.
jQuery, at its core, is a DOM (Document Object Model) manipulation library. The DOM is a tree-structure representation of all the elements of a Web page and jQuery simplifies the syntax for finding, selecting, and manipulating these DOM elements. For example, jQuery can be used for finding an element in the document with a certain property (e.g. all elements with an h1 tag), changing one or more of its attributes (e.g. color, visibility), or making it respond to an event (e.g. a mouse click).
jQuery also provides a paradigm for event handling that goes beyond basic DOM element selection and manipulation. The event assignment and the event callback function definition are done in a single step in a single location in the code. jQuery also aims to incorporate other highly used JavaScript functionality (e.g. fade ins and fade outs when hiding elements, animations by manipulating CSS properties)
jQuery's architecture allows developers to create plug-in code to extend its function. There are thousands of jQuery plug-ins available on the Web that cover a range of functions, such as Ajax helpers, Web services, datagrids, dynamic lists, XML and XSLT tools, drag and drop, events, cookie handling, and modal windows.
An important source of jQuery plug-ins is the plugins subdomain of the jQuery Project website. The plugins in this subdomain, however, were accidentally deleted in December 2011 in an attempt to rid the site of spam. The new site will include a GitHub-hosted repository, which will require developers to resubmit their plugins and to conform to new submission requirements. There are alternative plug-in search engines like jquer.in that take more specialized approaches, such as listing only plug-ins that meet certain criteria (e.g. those that have a public code repository). jQuery provides a "Learning Center" that can help users understand JavaScript and get started developing jQuery plugins.
jQuery was originally released in January 2006 at BarCamp NYC by John Resig and was influenced by Dean Edwards' earlier cssQuery library. It is currently maintained by a team of developers led by Timmy Willison (with the jQuery selector engine, Sizzle, being led by Richard Gibson).
jQuery has also an interesting software license history. Originally under the CC BY-SA 2.5, it was relicensed to the MIT license in 2006. On end of 2006 it was dual-licensed under GPL and MIT license. As this led to some confusion, in 2012 the GPL was dropped and is now only MIT licensed.
As of 2015, jQuery remains the most widely used JavaScript library on the Web. According to JavaScript library analytics service, Libscore, jQuery is in use on over 63% of the top million most popular sites by traffic volume. Notable sites using it include Twitter, LinkedIn, Pinterest, and eBay.