How jQuery Works jQuery Learning Center

You will go through installation of jQuery in a web project. Important web development concepts such as API, DOM, and CDN will be defined in relation to jQuery. Once you have this base of knowledge and jQuery installed, you will learn to use common selectors, events, and effects. It’s also bundled with some popular content management systems, including WordPress. In this example, version 3.6.0 of jQuery and your site-specific code in a file called my_script.js are located in the/js/ directory on the website.

What is jQuery

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, 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. Most of the current set of UI widgets follow the best practice of progressive enhancement and we’re working to extend that pattern to widgets that don’t.

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Selects elements that have the specified attribute, with any value. Selects all elements that are the first child of their parent. Select all elements that have no children (including text nodes). Selects all direct child elements specified by “child” of elements specified by “parent”. Remove a callback or a collection of callbacks from a callback list. Call all callbacks in a list with the given context and arguments.

  • Check to see if an object is empty (contains no enumerable properties).
  • The object is assigned to the constant reference content, then its textContent property is changed to “New text”.
  • No matter what technologies are the current favorites of developers, jQuery remains the most-used JavaScript library on the web.
  • Of course, this isn’t the only way to select elements; jQuery can use nearly any CSS selector, all packaged in its $ function.
  • If no elements match the provided selector, the new jQuery object is “empty”; that is, it contains no elements and has .length property of 0.
  • Bind an event handler to be fired when the mouse leaves an element, or trigger that handler on an element.

Elements will be copied from the array as-is and won’t be unwrapped if they’re already jQuery collections. Wrap an HTML structure around the content of each element in the set of matched elements. Remove the parents of the set of matched elements from the DOM, leaving the matched elements jquery development in their place. Execute all handlers and behaviors attached to the matched elements for the given event type. Remove an attribute from each element in the set of matched elements. Insert content, specified by the parameter, to the beginning of each element in the set of matched elements.


You can use the same approach to pull other jQuery components — like jQuery-UI — from a CDN. The jQuery library comes bundled with WordPress and is a key component of many WordPress themes. At the time, Mozilla’s new Firefox had a 10% market share (compared to Microsoft’s 84%) and Apple’s Safari had just appeared on the scene. JavaScript programmers like Resig regularly struggled to write code that would run in all browsers. StackOverflow’s 2022 survey of web technologies used by professional developers found that just over 29% of more than 45,000 respondents were working with jQuery. Among the JavaScript libraries, jQuery was second only to React.js, the library first developed at Facebook (now Meta) in 2011 and which is now embraced by over 44% of those developers.

Wrap an HTML structure around each element in the set of matched elements. Reduce the set of matched elements to a subset specified by a range of indices. Replace each target element with the set of matched elements. Insert every element in the set of matched elements to the beginning of the target. Reduce the set of matched elements to the odd ones in the set, numbered from zero.

You will begin this exercise by creating a small web project. It will consist of style.css in the css/ directory, scripts.js in the js/ directory, and a main index.html in the root of the project. For more than 15 years, the open-source jQuery library has helped developers build rich, dynamic web applications with as little coding as possible. Today, jQuery is used on more websites than any other JavaScript library. The jquery handle has been assigned to the jQuery library on the Cloudflare CDN and it remains a dependency for the local my_script.

JQuery’s architecture allows developers to create plug-in code to extend its function. At W3Schools you will find a complete reference of all jQuery selectors, methods, properties and events. Widgets should provide hooks to enable developers to customize both behavioral and presentational aspects. Class names used on internal elements should be meaningful to jQuery UI users and enable styling either through ThemeRoller or hand-written CSS via the jQuery UI CSS Framework. As much as possible, style attributes should be separated into the plugin’s CSS, not within the scripts in order to make customization simple and clear.

How to include jQuery file in HTML code?

Bind an event handler to the “change” event, or trigger that event on an element. Bind an event handler to the “blur” event, or trigger that event on an element. Add the previous set of elements on the stack to the current set, optionally filtered by a selector. It makes things like HTML document traversal and manipulation, event handling, animation, and Ajax much simpler with an easy-to-use API that works across a multitude of browsers.

What is jQuery

You’ll do this by editing the functions.php file that is part of your theme. A theme update can overwrite that file, so it’s a good practice to keep your changes safe by first creating a child theme and editing the functions.php file there. At the very least, create a manual WordPress backup before you proceed. It is good practice to wait for the document to be fully loaded and ready before working with it. This also allows you to have your JavaScript code before the body of your document, in the head section.


JQuery effects work hand-in-hand with events by allowing you to add animations and otherwise manipulate elements on the page. Selectors are how you tell jQuery which elements you want to work on. Most jQuery selectors are the same as what you’re familiar with in CSS, with a few jQuery-specific additions. You can view the full list of jQuery selectors on their official documentation pages. JQuery UI is a popular collection of plugins designed to enhance user interfaces.

What is jQuery

If a selector is provided, it retrieves the previous sibling only if it matches that selector. Get the ancestors of each element in the current set of matched elements, optionally filtered by a selector. Get all following siblings of each element in the set of matched elements, optionally filtered by a selector. Get the immediately following sibling of each element in the set of matched elements. If a selector is provided, it retrieves the next sibling only if it matches that selector. Check the current matched set of elements against a selector, element, or jQuery object and return true if at least one of these elements matches the given arguments.

jQuery Selectors

We attempt to make components accessible through the use of semantic HTML elements within components and following the guidelines specified in the WAI-ARIA spec. Any image-based actions within widgets should provide text equivalents (close icons, expand/collapse icons, etc. should have title attributes at the least). All widgets should be designed for simplicity, ease of use and aesthetics. Features should be pared down to focus on what is practical and commonly needed with a system for extending features through customization.