The Yahoo! User Interface Library (YUI) is a discontinued open-source JavaScript library for building richly interactive web applications using techniques such as Ajax, DHTML, and DOM scripting. YUI includes several core CSS resources. It is available under a BSD License. Development on YUI began in 2005 and Yahoo! properties such as My Yahoo! and the Yahoo! front page began using YUI in the summer of that year. YUI was released for public use in February 2006. It was actively developed by a core team of Yahoo! engineers.
In September 2009, Yahoo! released YUI 3, a new version of YUI rebuilt from the ground up to modernize the library and incorporate lessons learned from YUI 2. Among the enhancements are a CSS selector driven engine, like jQuery, for retrieving DOM elements, a greater emphasis on granularity of modules, a smaller seed file that loads other modules when necessary, and a variety of syntactic changes intended to make writing code faster and easier.
The YUI Library project at Yahoo! was founded by Thomas Sha and sponsored internally by Yahoo! co-founder Jerry Yang; its principal architects have been Sha, Adam Moore, and Matt Sweeney. The library's developers maintain the YUIBlog; the YUI community discusses the library and its implementations in its community forum.
On August 29, 2014, it was announced that active development of YUI by Yahoo! would end, citing the evolution of the JavaScript standards, steadily decreasing interest in large JavaScript libraries by developers, and the proliferation of server-side solutions. Future development will be limited to maintenance releases addressing issues that are "absolutely critical to Yahoo properties."
Features
The YUI Library is fully documented on its website; detailed API documentation accompanies the library download. It has six types of components: YUI core, utilities, UI controls, CSS components, developer tools, and build tools.
Core
The YUI Core is a light (31KB minified) set of tools for event management and DOM manipulation.
YUI Global Object
The YUI Global Object contains language utilities, a script loader, and other baseline infrastructure for YUI. Dom Collection Helps with common DOM scripting tasks, including element positioning and CSS style management. Event Utility Provides developers with easy and safe access to browser events (such as mouse clicks and key presses). It also provides the Custom Event object for publishing and subscribing to custom events.
Utilities
Animation
Helps create "effects" by animating the position, size, opacity or other characteristics of page elements. Browser History Manager Helps web applications use the browser's back button and bookmarking functionality. Connection Manager Helps manage XMLHttpRequest transactions in a cross-browser fashion. It has integrated support for form posts, error handling, callbacks and file uploading. Cookie Allows you to manage browser cookies and subcookies through a simple API. DataSource Provides a common configurable interface for other components to interact with different types of data, from simple JavaScript arrays to online servers over XHR. Drag and drop The YUI Drag and Drop Utility makes it easy to make elements "draggable" and to create drop targets that respond to drag events. Element Provides a wrapper for HTML elements in the DOM and makes simpler common tasks such as adding listeners, manipulating the DOM, and setting and getting attributes. Get The Get Utility supports the asynchronous loading of data and scripts through script nodes and the dynamic loading of external CSS files. ImageLoader YUI's ImageLoader allows you to defer the loading of images that are not visible in the viewport at the time the page loads. This can result in big performance boosts. JSON The JSON Utility provides methods for validation of incoming JSON data to verify that it is safe and methods to convert JavaScript data to a JSON-formatted string. These methods are based on Douglas Crockford's work at JSON.org. Resize Allows you to make any block-level HTML element resizable. Selector The YUI Selector Utility allows you to grab references to HTML elements via CSS3 selector syntax. YUI Loader YUI Loader is a client-side loader engine that can dynamically load any YUI component (and dependencies) on the fly.