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jQuery Notes for ProfessionalsjQuery® Notes for Professionals GoalKicker.com Free Programming Books Disclaimer This is an unocial free book created for educational purposes and is not aliated with ocial jQuery® group(s) or company(s). All trademarks and registered trademarks are the property of their respective owners 50+ pages of professional hints and tricks

Contents About 1 ................................................................................................................................................................................... Chapter 1: Getting started with jQuery 2 ............................................................................................................. Section 1.1: Getting Started 2 ........................................................................................................................................... Section 1.2: Avoiding namespace collisions 3 ................................................................................................................ Section 1.3: jQuery Namespace ("jQuery" and "$") 4 ................................................................................................... Section 1.4: Loading jQuery via console on a page that does not have it 5 .............................................................. Section 1.5: Include script tag in head of HTML page 5 ................................................................................................ Section 1.6: The jQuery Object 7 ..................................................................................................................................... Chapter 2: Selectors 8 .................................................................................................................................................... Section 2.1: Overview 8 ..................................................................................................................................................... Section 2.2: Types of Selectors 8 .................................................................................................................................... Section 2.3: Caching Selectors 10 ................................................................................................................................... Section 2.4: Combining selectors 11 ............................................................................................................................... Section 2.5: DOM Elements as selectors 13 ................................................................................................................... Section 2.6: HTML strings as selectors 13 ...................................................................................................................... Chapter 3: Each function 15 ........................................................................................................................................ Section 3.1: jQuery each function 15 ............................................................................................................................... Chapter 4: Attributes 16 ............................................................................................................................................... Section 4.1: Dierece between attr() and prop() 16 ..................................................................................................... Section 4.2: Get the attribute value of a HTML element 16 ......................................................................................... Section 4.3: Setting value of HTML attribute 17 ............................................................................................................ Section 4.4: Removing attribute 17 ................................................................................................................................ Chapter 5: document-ready event 18 .................................................................................................................... Section 5.1: What is document-ready and how should I use it? 18 ............................................................................. Section 5.2: jQuery 2.2.3 and earlier 18 .......................................................................................................................... Section 5.3: jQuery 3.0 19 ................................................................................................................................................. Section 5.4: Attaching events and manipulating the DOM inside ready() 19 ............................................................ Section 5.5: Dierence between $(document).ready() and $(window).load() 20 ..................................................... Section 5.6: Dierence between jQuery(fn) and executing your code before </body> 21 ..................................... Chapter 6: Events 22 ....................................................................................................................................................... Section 6.1: Delegated Events 22 .................................................................................................................................... Section 6.2: Attach and Detach Event Handlers 23 ...................................................................................................... Section 6.3: Switching specific events on and o via jQuery. (Named Listeners) 24 ................................................ Section 6.4: originalEvent 25 ........................................................................................................................................... Section 6.5: Events for repeating elements without using ID's 25 ............................................................................... Section 6.6: Document Loading Event .load() 26 .......................................................................................................... Chapter 7: DOM Manipulation 27 .............................................................................................................................. Section 7.1: Creating DOM elements 27 .......................................................................................................................... Section 7.2: Manipulating element classes 27 ............................................................................................................... Section 7.3: Other API Methods 29 .................................................................................................................................. Chapter 8: DOM Traversing 31 ................................................................................................................................... Section 8.1: Select children of element 31 ...................................................................................................................... Section 8.2: Get next element 31 .................................................................................................................................... Section 8.3: Get previous element 31 ............................................................................................................................. Section 8.4: Filter a selection 32 ...................................................................................................................................... Section 8.5: find() method 33 ..........................................................................................................................................

Section 8.6: Iterating over list of jQuery elements 34 ................................................................................................... Section 8.7: Selecting siblings 34 ..................................................................................................................................... Section 8.8: closest() method 34 ..................................................................................................................................... Chapter 9: CSS Manipulation 36 ................................................................................................................................ Section 9.1: CSS – Getters and Setters 36 ....................................................................................................................... Section 9.2: Increment/Decrement Numeric Properties 36 ......................................................................................... Section 9.3: Set CSS property 37 ..................................................................................................................................... Section 9.4: Get CSS property 37 .................................................................................................................................... Chapter 10: Element Visibility 38 ............................................................................................................................... Section 10.1: Overview 38 ................................................................................................................................................. Section 10.2: Toggle possibilities 38 ................................................................................................................................ Chapter 11: Append 40 .................................................................................................................................................... Section 11.1: Ecient consecutive .append() usage 40 .................................................................................................. Section 11.2: jQuery append 43 ....................................................................................................................................... Section 11.3: Appending an element to a container 43 ................................................................................................. Chapter 12: Prepend 45 .................................................................................................................................................. Section 12.1: Prepending an element to a container 45 ................................................................................................ Section 12.2: Prepend method 45 .................................................................................................................................... Chapter 13: Getting and setting width and height of an element 47 ..................................................... Section 13.1: Getting and setting width and height (ignoring border) 47 .................................................................... Section 13.2: Getting and setting innerWidth and innerHeight (ignoring padding and border) 47 ......................... Section 13.3: Getting and setting outerWidth and outerHeight (including padding and border) 47 ....................... Chapter 14: jQuery .animate() Method 48 ............................................................................................................ Section 14.1: Animation with callback 48 ........................................................................................................................ Chapter 15: jQuery Deferred objects and Promises 50 ................................................................................. Section 15.1: jQuery ajax() success, error VS .done(), .fail() 50 ..................................................................................... Section 15.2: Basic promise creation 50 ......................................................................................................................... Chapter 16: Ajax 52 ........................................................................................................................................................... Section 16.1: Handling HTTP Response Codes with $.ajax() 52 .................................................................................... Section 16.2: Using Ajax to Submit a Form 53 ............................................................................................................... Section 16.3: All in one examples 53 ................................................................................................................................ Section 16.4: Ajax File Uploads 55 ................................................................................................................................... Chapter 17: Checkbox Select all with automatic check/uncheck on other checkbox change 58 .............................................................................................................................................................................. Section 17.1: 2 select all checkboxes with corresponding group checkboxes 58 ....................................................... Chapter 18: Plugins 59 ..................................................................................................................................................... Section 18.1: Plugins - Getting Started 59 ....................................................................................................................... Credits 61 .............................................................................................................................................................................. You may also like 64 ........................................................................................................................................................

GoalKicker.com – jQuery® Notes for Professionals 1 About Please feel free to share this PDF with anyone for free, latest version of this book can be downloaded from: https://goalkicker.com/jQueryBook This jQuery® Notes for Professionals book is compiled from Stack Overflow Documentation, the content is written by the beautiful people at Stack Overflow. Text content is released under Creative Commons BY-SA, see credits at the end of this book whom contributed to the various chapters. Images may be copyright of their respective owners unless otherwise specified This is an unofficial free book created for educational purposes and is not affiliated with official jQuery® group(s) or company(s) nor Stack Overflow. All trademarks and registered trademarks are the property of their respective company owners The information presented in this book is not guaranteed to be correct nor accurate, use at your own risk Please send feedback and corrections to web@petercv.com

GoalKicker.com – jQuery® Notes for Professionals 2 Chapter 1: Getting started with jQuery Version Notes Release Date 1.0 First stable release 2006-08-26 1.1 2007-01-14 1.2 2007-09-10 1.3 Sizzle introduced into core 2009-01-14 1.4 2010-01-14 1.5 Deferred callback management, ajax module rewrite 2011-01-31 1.6 Significant performance gains in the attr() and val() methods 2011-05-03 1.7 New Event APIs: on() and off(). 2011-11-03 1.8 Sizzle rewritten, improved animations and $(html, props) flexibility. 2012-08-09 1.9 Removal of deprecated interfaces and code cleanup 2013-01-15 1.10 Incorporated bug fixes and differences reported from both the 1.9 and 2.0 beta cycles 2013-05-24 1.11 2014-01-24 1.12 2016-01-08 2.0 Dropped IE 6–8 support for performance improvements and reduction in size 2013-04-18 2.1 2014-01-24 2.2 2016-01-08 3.0 Massive speedups for some jQuery custom selectors 2016-06-09 3.1 No More Silent Errors 2016-07-07 3.2 No More Silent Errors 2017-03-16 3.3 No More Silent Errors 2018-01-19 Section 1.1: Getting Started Create a file hello.html with the following content: <!DOCTYPE html> <html> <head> <title>Hello, World!</title> </head> <body> <div> <p id="hello">Some random text</p> </div> <script src="https://code.jquery.com/jquery-2.2.4.min.js"></script> <script> $(document).ready(function() { $('#hello').text('Hello, World!'); }); </script> </body> </html> Live Demo on JSBin Open this file in a web browser. As a result you will see a page with the text: Hello, World! Explanation of code

GoalKicker.com – jQuery® Notes for Professionals 3 Loads the jQuery library from the jQuery CDN:1. <script src="https://code.jquery.com/jquery-2.2.4.min.js"></script> This introduces the $ global variable, an alias for the jQuery function and namespace. Be aware that one of the most common mistakes made when including jQuery is failing to load the library BEFORE any other scripts or libraries that may depend on or make use of it. Defers a function to be executed when the DOM (Document Object Model) is detected to be "ready" by2. jQuery: // When the `document` is `ready`, execute this function `...` $(document).ready(function() { ... }); // A commonly used shorthand version (behaves the same as the above) $(function() { ... }); Once the DOM is ready, jQuery executes the callback function shown above. Inside of our function, there is3. only one call which does 2 main things: Gets the element with the id attribute equal to hello (our selector #hello). Using a selector as the1. passed argument is the core of jQuery's functionality and naming; the entire library essentially evolved from extending document.querySelectorAllMDN. Set the text() inside the selected element to Hello, World!.2. # ↓ - Pass a `selector` to `$` jQuery, returns our element $('#hello').text('Hello, World!'); # ↑ - Set the Text on the element For more refer to the jQuery - Documentation page. Section 1.2: Avoiding namespace collisions Libraries other than jQuery may also use $ as an alias. This can cause interference between those libraries and jQuery. To release $ for use with other libraries: jQuery.noConflict(); After calling this function, $ is no longer an alias for jQuery. However, you can still use the variable jQuery itself to access jQuery functions: jQuery('#hello').text('Hello, World!'); Optionally, you can assign a different variable as an alias for jQuery: var jqy = jQuery.noConflict();

GoalKicker.com – jQuery® Notes for Professionals 4 jqy('#hello').text('Hello, World!'); Conversely, to prevent other libraries from interfering with jQuery, you can wrap your jQuery code in an immediately invoked function expression (IIFE) and pass in jQuery as the argument: (function($) { $(document).ready(function() { $('#hello').text('Hello, World!'); }); })(jQuery); Inside this IIFE, $ is an alias for jQuery only. Another simple way to secure jQuery's $ alias and make sure DOM is ready: jQuery(function( $ ) { // DOM is ready // You're now free to use $ alias $('#hello').text('Hello, World!'); }); To summarize, jQuery.noConflict() : $ no longer refers to jQuery, while the variable jQuery does. var jQuery2 = jQuery.noConflict() - $ no longer refers to jQuery, while the variable jQuery does and so does the variable jQuery2. Now, there exists a third scenario - What if we want jQuery to be available only in jQuery2? Use, var jQuery2 = jQuery.noConflict(true) This results in neither $ nor jQuery referring to jQuery. This is useful when multiple versions of jQuery are to be loaded onto the same page. <script src='https://code.jquery.com/jquery-1.12.4.min.js'></script> <script> var jQuery1 = jQuery.noConflict(true); </script> <script src='https://code.jquery.com/jquery-3.1.0.min.js'></script> <script> // Here, jQuery1 refers to jQuery 1.12.4 while, $ and jQuery refers to jQuery 3.1.0. </script> https://learn.jquery.com/using-jquery-core/avoid-conflicts-other-libraries/ Section 1.3: jQuery Namespace ("jQuery" and "$") jQuery is the starting point for writing any jQuery code. It can be used as a function jQuery(...) or a variable jQuery.foo. $ is an alias for jQuery and the two can usually be interchanged for each other (except where jQuery.noConflict(); has been used - see Avoiding namespace collisions). Assuming we have this snippet of HTML - <div id="demo_div" class="demo"></div>

GoalKicker.com – jQuery® Notes for Professionals 5 We might want to use jQuery to add some text content to this div. To do this we could use the jQuery text() function. This could be written using either jQuery or $. i.e. - jQuery("#demo_div").text("Demo Text!"); Or - $("#demo_div").text("Demo Text!"); Both will result in the same final HTML - <div id="demo_div" class="demo">Demo Text!</div> As $ is more concise than jQuery it is the generally the preferred method of writing jQuery code. jQuery uses CSS selectors and in the example above an ID selector was used. For more information on selectors in jQuery see types of selectors. Section 1.4: Loading jQuery via console on a page that does not have it Sometimes one has to work with pages that are not using jQuery while most developers are used to have jQuery handy. In such situations one can use Chrome Developer Tools console ( F12 ) to manually add jQuery on a loaded page by running following: var j = document.createElement('script'); j.onload = function(){ jQuery.noConflict(); }; j.src = "https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"; document.getElementsByTagName('head')[0].appendChild(j); Version you want might differ from above(1.12.4) you can get the link for one you need here. Section 1.5: Include script tag in head of HTML page To load jQuery from the official CDN, go to the jQuery website. You'll see a list of different versions and formats available.

GoalKicker.com – jQuery® Notes for Professionals 6 Now, copy the source of the version of jQuery, you want to load. Suppose, you want to load jQuery 2.X, click uncompressed or minified tag which will show you something like this: Copy the full code (or click on the copy icon) and paste it in the <head> or <body> of your html. The best practice is to load any external JavaScript libraries at the head tag with the async attribute. Here is a demonstration: <!DOCTYPE html> <html> <head> <title>Loading jquery-2.2.4</title> <script src="https://code.jquery.com/jquery-2.2.4.min.js" async></script> </head> <body> <p>This page is loaded with jquery.</p> </body> </html>

GoalKicker.com – jQuery® Notes for Professionals 7 When using async attribute be conscious as the javascript libraries are then asynchronously loaded and executed as soon as available. If two libraries are included where second library is dependent on the first library is this case if second library is loaded and executed before first library then it may throw an error and application may break. Section 1.6: The jQuery Object Every time jQuery is called, by using $() or jQuery(), internally it is creating a new instance of jQuery. This is the source code which shows the new instance: // Define a local copy of jQuery jQuery = function( selector, context ) { // The jQuery object is actually just the init constructor 'enhanced' // Need init if jQuery is called (just allow error to be thrown if not included) return new jQuery.fn.init( selector, context ); } Internally jQuery refers to its prototype as .fn, and the style used here of internally instantiating a jQuery object allows for that prototype to be exposed without the explicit use of new by the caller. In addition to setting up an instance (which is how the jQuery API, such as .each, children,filter, etc. is exposed), internally jQuery will also create an array-like structure to match the result of the selector (provided that something other than nothing, undefined, null, or similar was passed as the argument). In the case of a single item, this array- like structure will hold only that item. A simple demonstration would be to find an element with an id, and then access the jQuery object to return the underlying DOM element (this will also work when multiple elements are matched or present). var $div = $("#myDiv");//populate the jQuery object with the result of the id selector var div = $div[0];//access array-like structure of jQuery object to get the DOM Element

GoalKicker.com – jQuery® Notes for Professionals 8 Chapter 2: Selectors A jQuery selectors selects or finds a DOM (document object model) element in an HTML document. It is used to select HTML elements based on id, name, types, attributes, class and etc. It is based on existing CSS selectors. Section 2.1: Overview Elements can be selected by jQuery using jQuery Selectors. The function returns either an element or a list of elements. Basic selectors $("*") // All elements $("div") // All <div> elements $(".blue") // All elements with class=blue $(".blue.red") // All elements with class=blue AND class=red $(".blue,.red") // All elements with class=blue OR class=red $("#headline") // The (first) element with id=headline $("[href]") // All elements with an href attribute $("[href='example.com']") // All elements with href=example.com Relational operators $("div span") // All <span>s that are descendants of a <div> $("div > span") // All <span>s that are a direct child of a <div> $("a ~ span") // All <span>s that are siblings following an <a> $("a + span") // All <span>s that are immediately after an <a> Section 2.2: Types of Selectors In jQuery you can select elements in a page using many various properties of the element, including: Type Class ID Possession of Attribute Attribute Value Indexed Selector Pseudo-state If you know CSS selectors you will notice selectors in jQuery are the same (with minor exceptions). Take the following HTML for example: <a href="index.html"></a> <!-- 1 --> <a id="second-link"></a> <!-- 2 --> <a class="example"></a> <!-- 3 --> <a class="example" href="about.html"></a> <!-- 4 --> <span class="example"></span> <!-- 5 --> Selecting by Type: The following jQuery selector will select all <a> elements, including 1, 2, 3 and 4. $("a")

GoalKicker.com – jQuery® Notes for Professionals 9 Selecting by Class The following jQuery selector will select all elements of class example (including non-a elements), which are 3, 4 and 5. $(".example") Selecting by ID The following jQuery selector will select the element with the given ID, which is 2. $("#second-link") Selecting by Possession of Attribute The following jQuery selector will select all elements with a defined href attribute, including 1 and 4. $("[href]") Selecting by Attribute Value The following jQuery selector will select all elements where the href attribute exists with a value of index.html, which is just 1. $("[href='index.html']") Selecting by Indexed Position (Indexed Selector) The following jQuery selector will select only 1, the second <a> ie. the second-link because index supplied is 1 like eq(1) (Note that the index starts at 0 hence the second got selected here!). $("a:eq(1)") Selecting with Indexed Exclusion To exclude an element by using its index :not(:eq()) The following selects <a> elements, except that with the class example, which is 1 $("a").not(":eq(0)") Selecting with Exclusion To exclude an element from a selection, use :not() The following selects <a> elements, except those with the class example, which are 1 and 2. $("a:not(.example)") Selecting by Pseudo-state You can also select in jQuery using pseudo-states, including :first-child, :last-child, :first-of-type, :last- of-type, etc. The following jQuery selector will only select the first <a> element: number 1.

GoalKicker.com – jQuery® Notes for Professionals 10 $("a:first-of-type") Combining jQuery selectors You can also increase your specificity by combining multiple jQuery selectors; you can combine any number of them or combine all of them. You can also select multiple classes, attributes and states at the same time. $("a.class1.class2.class3#someID[attr1][attr2='something'][attr3='something']:first-of-type:first- child") This would select an <a> element that: Has the following classes: class1, class2, and class3 Has the following ID: someID Has the following Attribute: attr1 Has the following Attributes and values: attr2 with value something, attr3 with value something Has the following states: first-child and first-of-type You can also separate different selectors with a comma: $("a, .class1, #someID") This would select: All <a> elements All elements that have the class class1 An element with the id #someID Child and Sibling selection jQuery selectors generally conform to the same conventions as CSS, which allows you to select children and siblings in the same way. To select a non-direct child, use a space To select a direct child, use a > To select an adjacent sibling following the first, use a + To select a non-adjacent sibling following the first, use a ~ Wildcard selection There might be cases when we want to select all elements but there is not a common property to select upon (class, attribute etc). In that case we can use the * selector that simply selects all the elements: $('#wrapper *') // Select all elements inside #wrapper element Section 2.3: Caching Selectors Each time you use a selector in jQuery the DOM is searched for elements that match your query. Doing this too often or repeatedly will decrease performance. If you refer to a specific selector more than once you should add it to the cache by assigning it to a variable: var nav = $('#navigation'); nav.show();

GoalKicker.com – jQuery® Notes for Professionals 11 This would replace: $('#navigation').show(); Caching this selector could prove helpful if your website needs to show/hide this element often. If there are multiple elements with the same selector the variable will become an array of these elements: <div class="parent"> <div class="child">Child 1</div> <div class="child">Child 2</div> </div> <script> var children = $('.child'); var firstChildText = children[0].text(); console.log(firstChildText); // output: "Child 1" </script> NOTE: The element has to exist in the DOM at the time of its assignment to a variable. If there is no element in the DOM with a class called child you will be storing an empty array in that variable. <div class="parent"></div> <script> var parent = $('.parent'); var children = $('.child'); console.log(children); // output: [] parent.append('<div class="child">Child 1</div>'); children = $('.child'); console.log(children[0].text()); // output: "Child 1" </script> Remember to reassign the selector to the variable after adding/removing elements in the DOM with that selector. Note: When caching selectors, many developers will start the variable name with a $ to denote that the variable is a jQuery object like so: var $nav = $('#navigation'); $nav.show(); Section 2.4: Combining selectors Consider following DOM Structure <ul class="parentUl"> <li> Level 1 <ul class="childUl"> <li>Level 1-1 <span> Item - 1 </span></li> <li>Level 1-1 <span> Item - 2 </span></li> </ul> </li>

GoalKicker.com – jQuery® Notes for Professionals 12 <li> Level 2 <ul class="childUl"> <li>Level 2-1 <span> Item - 1 </span></li> <li>Level 2-1 <span> Item - 1 </span></li> </ul> </li> </ul> Descendant and child selectors Given a parent <ul> - parentUl find its descendants (<li>), Simple $('parent child')1. >> $('ul.parentUl li') This gets all matching descendants of the specified ancestor all levels down. > - $('parent > child')2. >> $('ul.parentUl > li') This finds all matching children (only 1st level down). Context based selector - $('child','parent')3. >> $('li','ul.parentUl') This works same as 1. above. find() - $('parent').find('child')4. >> $('ul.parentUl').find('li') This works same as 1. above. children() - $('parent').find('child')5. >> $('ul.parentUl').children('li') This works same as 2. above. Other combinators Group Selector : "," Select all <ul> elements AND all <li> elements AND all <span> elements : $('ul, li, span') Multiples selector : "" (no character)

GoalKicker.com – jQuery® Notes for Professionals 13 Select all <ul> elements with class parentUl : $('ul.parentUl') Adjacent Sibling Selector : "+" Select all <li> elements that are placed immediately after another <li> element: $('li + li') General Sibling Selector : "~" Select all <li> elements that are siblings of other <li> elements: $('li ~ li') Section 2.5: DOM Elements as selectors jQuery accepts a wide variety of parameters, and one of them is an actual DOM element. Passing a DOM element to jQuery will cause the underlying array-like structure of the jQuery object to hold that element. jQuery will detect that the argument is a DOM element by inspecting its nodeType. The most common use of a DOM element is in callbacks, where the current element is passed to the jQuery constructor in order to gain access to the jQuery API. Such as in the each callback (note: each is an iterator function). $(".elements").each(function(){ //the current element is bound to `this` internally by jQuery when using each var currentElement = this; //at this point, currentElement (or this) has access to the Native API //construct a jQuery object with the currentElement(this) var $currentElement = $(this); //now $currentElement has access to the jQuery API }); Section 2.6: HTML strings as selectors jQuery accepts a wide variety of parameters as "selectors", and one of them is an HTML string. Passing an HTML string to jQuery will cause the underlying array-like structure of the jQuery object to hold the resulting constructed HTML. jQuery uses regex to determine if the string being passed to the constructor is an HTMLstring, and also that it must start with <. That regex is defined as rquickExpr = /^(?:\s*(<[\w\W]+>)[^>]*|#([\w-]*))$/ (explanation at regex101.com). The most common use of an HTML string as a selector is when sets of DOM elements need to be created in code only, often this is used by libraries for things like Modal popouts. For example, a function which returned an anchor tag wrapped in a div as a template function template(href,text){ return $("<div><a href='" + href + "'>" + text + "</a></div>");

GoalKicker.com – jQuery® Notes for Professionals 14 } Would return a jQuery object holding <div> <a href="google.com">Google</a> </div> if called as template("google.com","Google").

GoalKicker.com – jQuery® Notes for Professionals 15 Chapter 3: Each function Section 3.1: jQuery each function HTML: <ul> <li>Mango</li> <li>Book</li> </ul> Script: $( "li" ).each(function( index ) { console.log( index + ": " + $( this ).text() ); }); A message is thus logged for each item in the list: 0: Mango 1: Book

GoalKicker.com – jQuery® Notes for Professionals 16 Chapter 4: Attributes Section 4.1: Dierece between attr() and prop() attr() gets/sets the HTML attribute using the DOM functions getAttribute() and setAttribute(). prop() works by setting the DOM property without changing the attribute. In many cases the two are interchangeable, but occasionally one is needed over the other. To set a checkbox as checked: $('#tosAccept').prop('checked', true); // using attr() won't work properly here To remove a property you can use the removeProp() method. Similarly removeAttr() removes attributes. Section 4.2: Get the attribute value of a HTML element When a single parameter is passed to the .attr() function it returns the value of passed attribute on the selected element. Syntax: $([selector]).attr([attribute name]); Example: HTML: <a href="/home">Home</a> jQuery: $('a').attr('href'); Fetching data attributes: jQuery offers .data() function in order to deal with data attributes. .data function returns the value of the data attribute on the selected element. Syntax: $([selector]).data([attribute name]); Example: Html: <article data-column="3"></article> jQuery: $("article").data("column") Note: jQuery's data() method will give you access to data-* attributes, BUT, it clobbers the case of the attribute name. Reference

GoalKicker.com – jQuery® Notes for Professionals 17 Section 4.3: Setting value of HTML attribute If you want to add an attribute to some element you can use the attr(attributeName, attributeValue) function. For example: $('a').attr('title', 'Click me'); This example will add mouseover text "Click me" to all links on the page. The same function is used to change attributes' values. Section 4.4: Removing attribute To remove an attribute from an element you can use the function .removeAttr(attributeName). For example: $('#home').removeAttr('title'); This will remove title attribute from the element with ID home.