YUI has been discontinued. Similar apps include jQuery, which is free and open source. Other options are Dojo Toolkit, Umbrella JS, Prototype JS and smaloa. In total there are seven JavaScript Frameworks like YUI for the web and self-hosting.
jQuery is a fast, small, and feature-rich JavaScript library. 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.
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Dojo Toolkit is an open source modular JavaScript library (or more specifically JavaScript toolkit) designed to ease the rapid development of cross-platform, JavaScript/Ajax-based applications and web sites.
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Prototype is a JavaScript Framework that aims to ease development of dynamic web applications. Prototype provides various functions for developing JavaScript applications. The features range from programming shortcuts to major functions for dealing with XMLHttpRequest.
smaloa is an easy yet powerful javascript library mainly used for DOM processing, visual effects and project structuring. Easy to learn and hard to master.
Want to use Vanilla JS but find native APIs a bit unwieldy? Bliss is for you.
PKIjs is a pure JavaScript library implementing the formats that are used in PKI applications (signing, encryption, certificate requests, OCSP and TSP requests/responses). It is built on WebCrypto (Web Cryptography API) and requires no plug-ins.
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