MooTools is an open-source JavaScript framework designed for building powerful web applications using the object-oriented programming (OOP) approach. It is built on top of the Prototype JavaScript Framework, and uses a syntax similar to that of Java and C#. MooTools provides developers with a comprehensive set of tools for creating powerful web applications. It offers many features such as a powerful selector engine, cross-browser compatibility, AJAX utility, DOM manipulation, and more. It also comes with a library of plugins and tools that can help developers to quickly and easily create powerful web applications. MooTools is lightweight and fast, making it an ideal choice for developers who want to create robust web applications without the need for additional libraries or frameworks.
Discontinued by website: "IMPORTANT: YUI library is no longer actively maintained". Visit http://yuilibrary.com/