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jQuery
[ temporary import ]
please note:
- the content below is remote from Wikipedia
- it has been imported raw for GetWiki
{{short description|JavaScript library}}{{lowercase title}}







factoids
| latest preview version = | latest preview date = | programming language = JavaScript|Browser support}}| genre = JavaScript libraryMIT License>MITWEB
,weblink
, jQuery Project License
, 2017-03-11
, jQuery Foundation
, weblink}}| size = 30–263 KB}}jQuery is a JavaScript library designed to simplify HTML DOM tree traversal and manipulation, as well as event handling, CSS animation, and Ajax.WEB, urljquery.com/, jQuery: The write less, do more, JavaScript library, The jQuery Project, 29 April 2010, It is free, open-source software using the permissive MIT License. Web analysis (from 2017) indicates that it is the most widely deployed JavaScript library by a large margin.WEB, https:w3techs.com/technologies/overview/javascript_library/all, Usage of JavaScript libraries for websites, 2019-04-15, 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."Selectors API Level 1, W3C Recommendation" (21 February 2013). This standard turned what was jQuery "helper methods" into JavaScript-native ones, and the wide use of jQuery stimulated the fast adoption of querySelector/querySelectorAll into main Web browsers.Microsoft and Nokia bundle jQuery on their platforms.WEB, urljquery.com/blog/2008/09/28/jquery-microsoft-nokia/, jQuery, Microsoft, and Nokia, 2008-09-28, Resig, John, jQuery, jQuery Blog, 2009-01-29, Microsoft includes it with Visual StudioWEB, https:weblogs.asp.net/scottgu/jquery-and-microsoft, jQuery and Microsoft, Guthrie, Scott, ScottGu's Blog, 2008-09-28, 2019-04-15, 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.WEB,weblink Guarana UI: A jQuery Based UI Library for Nokia WRT, Forum Nokia,weblink" title="web.archive.org/web/20110816054350weblink">weblink 2009-11-23, yes, 2010-03-30,

Overview

jQuery, at its core, is a Document Object Model (DOM) manipulation library. The DOM is a tree-structure representation of all the elements of a Web page. 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).The principles of developing with jQuery are:
  • Separation of JavaScript and HTML: The jQuery library provides simple syntax for adding event handlers to the DOM using JavaScript, rather than adding HTML event attributes to call JavaScript functions. Thus, it encourages developers to completely separate JavaScript code from HTML markup.
  • Brevity and clarity: jQuery promotes brevity and clarity with features like "chainable" functions and shorthand function names.
  • Elimination of cross-browser incompatibilities: The JavaScript engines of different browsers differ slightly so JavaScript code that works for one browser may not work for another. Like other JavaScript toolkits, jQuery handles all these cross-browser inconsistencies and provides a consistent interface that works across different browsers.
  • Extensibility: New events, elements, and methods can be easily added and then reused as a plugin.

History

jQuery was originally created in January 2006 at BarCamp NYC by John Resig, influenced by Dean Edwards' earlier cssQuery library.BOOK, York, Richard, Beginning JavaScript and CSS Development with jQuery, 28, Wiley, 978-0-470-22779-4, 2009, L9otyT4crSQC&pg=PA515, WEB, https:www.slideshare.net/jeresig/history-of-jquery, History of jQuery, 2007-10-31first=Johndate=August 2018}}jQuery was originally licensed under the CC BY-SA 2.5, and relicensed to the MIT license in 2006.jquery-under-the-mit-license on jquery.org (2006) At the end of 2006, it was dual-licensed under GPL and MIT licenses.weblink" title="web.archive.org/web/20100301130833weblink">license on jquery.org (archived 2010) As this led to some confusion, in 2012 the GPL was dropped and is now only licensed under the MIT license.jquery-licensing-changes on jquery.org (2012) In 2015, jQuery was used on 63% of the top 1 million websites (according to BuiltWith), and 17% of all Internet websites.WEB,weblink Handling 15,000 requests per second: The Growth Behind jQuery, 20 June 2015, www.maxcdn.com, MaxCDN, en-US, 2018-07-02, As of June 2018, jQuery is used on 73% of the top 1 million websites, and by 22.4% of all websites (according to BuiltWith).WEB,weblink jQuery Usage Statistics, trends.builtwith.com, en, 2018-07-02,

Features

jQuery includes the following features:
  • DOM element selections using the multi-browser open source selector engine Sizzle, a spin-off of the jQuery projectWEB, jQuery 1.3 and the jQuery Foundation,weblink Resig, John, 2009-01-14, jQuery Blog, 2009-05-04,
  • DOM manipulation based on CSS selectors that uses elements' names and attributes, such as id and class, as criteria to select nodes in the DOM
  • Events
  • Effects and animations
  • Ajax
  • Deferred and Promise objects to control asynchronous processing
  • JSON parsing
  • Extensibility through plug-ins
  • Utilities, such as feature detection
  • Compatibility methods that are natively available in modern browsers, but need fallbacks for older browsers, such as jQuery.inArray() and jQuery.each().
  • Cross-browser support

Browser support

jQuery 3.0 & newer supports "current−1 versions" (meaning the current stable version of the browser and the version that preceded it) of Firefox (and ESR), Chrome, Safari, and Edge as well as Internet Explorer 9 & newer. On mobile it supports iOS 7 & newer and Android 4.0 & newer.[//jquery.com/browser-support/ Browser Support | jQuery]

Distribution

The jQuery library is typically distributed as a single JavaScript file that defines all its interfaces, including DOM, Events, and Ajax functions. It can be included within a Web page by linking to a local copy, or by linking to one of the many copies available from public servers. jQuery has a content delivery network (CDN) hosted by MaxCDN.WEB,weblink jQuery CDN, jQuery Foundation -, jquery.org, Google in Google Hosted Libraries service and Microsoft host the library as well.WEB,weblink Google Libraries API - Developer's Guide, code.google.com, March 11, 2012, WEB,weblink Microsoft Ajax Content Delivery Network, Microsoft Corporation, ASP.net, 2019-04-15, Example of linking a copy of the library locally (from the same server that hosts the Web page):Example of linking a copy of the library from jQuery's public CDN:

Interface

Functions

jQuery provides two kinds of functions, static utility functions and jQuery object methods. Each has its own usage style.Both are accessed through jQuery's main identifier: jQuery. This identifier has an alias named $WEB,weblink jQuery() {{!, jQuery API Documentation|last=js.foundation|first=JS Foundation -|website=api.jquery.com|language=en-US|access-date=2018-07-02}}. All functions can be accessed through either of these two names.

jQuery methods

The jQuery function is a factory for creating a jQuery object that represents one or more DOM nodes. jQuery objects have methods to manipulate these nodes. These methods (sometimes called commands), are chainable as each method also returns a jQuery object.Access to and manipulation of multiple DOM nodes in jQuery typically begins with calling the $ function with a CSS selector string. This returns a jQuery object referencing all the matching elements in the HTML page. $("div.test"), for example, returns a jQuery object with all the div elements of class test. This node set can be manipulated by calling methods on the returned jQuery object.

Static utilities

These are utility functions and do not directly act upon a jQuery object. They are accessed as static methods on the jQuery or $ identifier. For example, $.ajax() is a static method.

No-conflict mode

jQuery provides a $.noConflict() function, which relinquishes control of the $ name. This is useful if jQuery is used on a Web page also linking another library that demands the $ symbol as its identifier. In no-conflict mode, developers can use jQuery as a replacement for $ without losing functionality.WEB, //api.jquery.com/jquery.noconflict/, jQuery.noConflict() jQuery API Documentation,

Typical start-point

Typically, jQuery is used by putting initialization code and event handling functions in $(handler). This is triggered by jQuery when the browser has finished constructing the DOM for the current Web page.$(function () {
// This anonymous function is called when the page has completed loading.
// Here, one can place code to create jQuery objects, handle events, etc.
});or$(fn); // The function named fn, defined elsewhere, is called when the page has loaded.Historically, $(document).ready(callback) has been the de-facto idiom for running code after the DOM is ready. However, since jQuery 3.0, developers are encouraged to use the much shorter $(handler) signature instead.WEB,weblink jQuery Core 3.0 Upgrade Guide - jQuery, jQuery Foundation -, jquery.org,

Chaining

jQuery object methods typically also return a jQuery object, which enables the use of method chains:$('div.test')
.on('click', handleTestClick)
.addClass('foo');
This line finds all div element with class attribute test , then registers an event handler on each element for the "click" event, then adds the class attribute foo to each element.Certain jQuery object methods retrieve specific values (instead of modifying state). An example of this is the val() method, which returns the current value of a text input element. In these cases, a statement such as $('#user-email').val() cannot be used for chaining as the return value does not reference a jQuery object.

Creating new DOM elements

Besides accessing existing DOM nodes through jQuery, it is also possible to create new DOM nodes, if the string passed as the argument to $() factory looks like HTML. For example, the below code finds an HTML select element, and creates a new option element with value "VAG" and label "Volkswagen", which is then appended to the select menu:$('select#car-brands')
.append($('')
.attr({ value: 'VAG' })
.text('Volkswagen')
);

Ajax

It is possible to make Ajax requests (with cross-browser support) with $.ajax() to load and manipulate remote data.$.ajax({
type: 'POST',
url: '/process/submit.php',
data: {
name : 'John',
location : 'Boston',
},
}).then(function(msg) {
alert('Data Saved: ' + msg);
}).catch(function(xmlHttpRequest, statusText, errorThrown) {
alert(
'Your form submission failed.nn'
+ 'XML Http Request: ' + JSON.stringify(xmlHttpRequest)
+ ',nStatus Text: ' + statusText
+ ',nError Thrown: ' + errorThrown);
});This example posts the data name=John and location=Boston to /process/submit.php on the server. When this request finishes the success function is called to alert the user. If the request fails it will alert the user to the failure, the status of the request, and the specific error.The above example uses the .then() and .catch() methods to register callbacks that run when the response has completed. These promise callbacks must be used due to the asynchronous nature of Ajax requests.

jQuery plug-ins

jQuery's architecture allows developers to create plug-in code to extend its function. There are thousands of jQuery plug-ins available on the WebWEB, Plugins,weblink The jQuery Project, 2019-04-15, 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 sub-domain 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.WEB,weblink What Is Happening To The jQuery Plugins Site?, jQuery Blog, 22 April 2015, The new site is a GitHub-hosted repository, which required developers to resubmit their plugins and to conform to new submission requirements.WEB,weblink jquery/plugins.jquery.com, GitHub, 22 April 2015, jQuery provides a "Learning Center" that can help users understand JavaScript and get started developing jQuery plugins.WEB, jQuery Learning Center, //learn.jquery.com/, jQuery Foundation, 2014-07-02,

Release history{| class"wikitable sortable"

! Version number! Release date! Latest update! Size Prod (KB)! Additional notes| 1.0| 1.1| 1.2| 1.3| 1.4| 1.5| 1.6| 1.7| 1.8| 1.9201304}})| 90.5| Removal of deprecated interfaces and code cleanup| 1.10| 1.11| 1.12| 2.0| 2.1| 2.2| 3.0TITLE=LONG-AWAITED JQUERY 3.0 BRINGS SLIM BUILDFIRST=JAMESPUBLISHER=INFOQ.COM, 2017-01-28, | 3.1| 3.2WORK=JQUERY BLOGACCESSDATE=12 MARCH 2018, 16 March 2017, | 3.3WORK=JQUERY BLOGACCESSDATE=2019-04-15, 2018-01-19, WORK=JQUERY BLOGACCESSDATE=2019-04-15, 2018-01-20, | 84.9| Deprecation of old functions, functions that accept classes now also support them in array format.|3.4WORK=JQUERY BLOGACCESSDATE=2019-04-15, 2018-04-10, |3.4.0 (April 10, 2019)|86.1| Performance improvements, nonce and nomodule support, fixes for radio elements, a minor security fix

Testing framework

QUnit is a test automation framework used to test the jQuery project. The jQuery team developed it as an in-house unit testing library.WEB,weblink History, 2019-04-15, qunitjs.com, The jQuery team uses it to test its code and plugins, but it can test any generic JavaScript code, including server-side JavaScript code.As of 2011, the jQuery Testing Team uses QUnit with TestSwarm to test each jQuery codebase release.WEB,weblink jQuery Testing Team Wiki,

See also

References

{{Reflist}}

Further reading

  • VIDEO


,weblink
, John Resig: Advancing JavaScript with Libraries
, John Resig (speaker)
, YouTube video
, YUI Theater
, 2007-04-13
, 2018-01-09
,
  • WEB


, JavaScript, .Net developers aided in separate project
, Krill, Paul
, InfoWorld
,weblink
, 2006-08-31
, 2019-04-15
,
  • WEB


, jQuery Eases JavaScript, AJAX Development
, Taft, Darryl K.
, eWeek
,weblink
, 2006-08-30
, 2019-04-15
,

External links

{{Commons category|JQuery}}
  • {{Official website|//jquery.com}}
{{ECMAScript}}{{Application frameworks}}{{Widget toolkits}}{{Authority control}}

- content above as imported from Wikipedia
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- time: 2:26pm EDT - Thu, Apr 25 2019
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