Great Javascript frameworks
Javascript is and has been the best client side scripting language so far. I increases the usability and reduce the server resource usage when used wisely. Ajax is a technology built around Javascript and that alone has greatly advanced the web based applications.
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Though we can code in pure javascript there are some Javascript frameworks that ease the development. Thease are;

Prototype
Prototype is one of the earlier Javascript frameworks and is also included in the Ruby on Rails framework. It aims to ease development of dynamic web applications. Featuring a unique, easy-to-use toolkit for class-driven development and the nicest Ajax library around, Prototype is quickly becoming the codebase of choice for web application developers everywhere.
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JQuery
JQuery is a framework that has received a lot of attention due to its speed, size and smart modular approach which has led to a big library of plugins. jQuery is a fast, concise, JavaScript Library that simplifies how you traverse HTML documents, handle events, perform animations, and add Ajax interactions to your web pages. jQuery is designed to change the way that you write JavaScript.
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MooTools
Just like other Javascript frameworks, MooTools contains several functions to help development. One of the more known ones is its advanced effects component. MooTools is a compact, modular, Object-Oriented JavaScript framework designed for the intermediate to advanced JavaScript developer. It allows you to write powerful, flexible, and cross-browser code with its elegant, well documented, and coherent API. MooTools code respects strict standards and doesn’t throw any warnings. It’s extensively documented and has meaningful variable names: a joy to browse and a snap to understand.
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Yahoo! UI Library (YUI)
Yahoo has developed its own Javascript framework. They use it for their own websites, but have also made it freely available to others. This user Interface (YUI) Library is a set of utilities and controls, written in JavaScript, for building richly interactive web applications using techniques such as DOM scripting, DHTML and AJAX. The YUI Library also includes several core CSS resources. All components in the YUI Library have been released as open source under a BSD license and are free for all uses.
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