When developing a responsively designed web site, it is likely that you will come across a situation where you will want to selectively execute a JavaScript callback based on a media query comparison. For example, you may want to alter your menu layout for small-screen devices. Or you may wish to load in specific content only on large-screen devices. Luckily, these capabilities are currently available. In this article I will cover a couple methods and show you that this can be done without much trouble at all!