HeadJS

HeadJS is a JavaScript library for managing script loading and detecting browser capabilities. It provides conditional loading of JavaScript files based on browser features, allowing developers to load polyfills only when needed. HeadJS includes responsive design helpers for detecting screen sizes and applying CSS classes based on viewport dimensions. The library offers methods for loading scripts in parallel while maintaining execution order, improving page load performance. It includes feature detection capabilities similar to Modernizr but with a smaller footprint. While less commonly used in modern development due to native module loading and CSS media queries, HeadJS is still found in legacy projects requiring dynamic script management.