matchMedia() polyfill

matchMedia() polyfill is a JavaScript polyfill that brings matchMedia-style media query testing to environments that need compatibility support. It lets developers test whether a CSS media type or media query applies directly from JavaScript. The library is useful for responsive behavior that depends on screen size, device type, orientation, or other media query conditions. It can be used with a companion addListener polyfill when code needs to react to changes over time. The project was used by tools such as Respond.js, FormFactor, and Modernizr, which reflects its role in older responsive web development workflows. It is most relevant for legacy browser support, educational reference, and projects that need to understand how JavaScript-based media query testing worked before broad native support.