loglevel : Minimal lightweight logging for JavaScript, adding reliable log level methods to wrap any available console.log methods
script.aculo.us : script.aculo.us provides you with
easy-to-use, cross-browser user
interface JavaScript libraries to make
your web sites and web applications fly.
JavaScript Templates : For web application developers, the '''JavaScript Templates''' engine from TrimPath is a lightweight APL / GPL open-source component that lets you hav...
Dropzone.js : DropzoneJS is an open source library that provides drag'n'drop file uploads with image previews.
Ink : Ink provides the same component-based UI building experience that React offers in the browser, but for command-line apps. It uses Yoga to build Flexbo...
TogetherJS is a free, open source JavaScript library by Mozilla that adds collaboration features and tools to your website. By adding TogetherJS to your site, your users can help each other out on a website in real time!