YUI (Yahoo! User Interface Library) is a free, open source JavaScript library created by Yahoo! that helps developers build dynamic, interactive web applications using the latest web technologies such as HTML5, CSS3, and JavaScript. It provides a powerful set of tools and resources to help developers create interactive websites and applications without having to write a lot of code. With YUI, developers can create applications that are fast and reliable, and can be easily integrated into existing websites and applications. YUI also provides an extensive library of widgets, including a drag-and-drop library, a charting library, and a variety of user interface components. Additionally, YUI is constantly updated with new features and bug fixes, making it an ideal choice for any web development project.
YUI is much more than a DOM manipulation tool, it features complex widgets and tools for dialog panels, data tables, drag-and-drop elements, and so on. Even the prolific jQuery library is a poor comparison without jQueryUI and a host of other plugins.