Facebook Pixel helps organizations measure customer actions, build audiences and unlock optimisation tools. Facebook pixel is a snippet of JavaScript code that allows you to track visitor activity on your website.
Modernizr is a JavaScript library which is designed to detect HTML5 and CSS3 features in various browsers, which lets JavaScript avoid using unimplemented features or use a workaround such as a shim to emulate them. Modernizr aims to provide this feature detection in a complete and standardized manner.
The Prototype JavaScript Framework is a JavaScript framework as part of the foundation for Ajax support in Ruby on Rails. It is implemented as a single file of JavaScript code, usually named prototype.js.