Linking CSS breakpoints to JavaScript

Typically, with something web-based involving any sort of interaction, JavaScript will be involved. When you're developing a responsive project, it's feasible that you will want to do different things at different viewport sizes. Not just in CSS but also in JavaScript.

Let's suppose we want to invoke a certain JavaScript function when we reach a certain breakpoint in the CSS (remember that "breakpoint" is the term used to define the point in which a responsive design should change significantly). Let's suppose the breakpoint is 47.5rem (with a 16px root font size that would equate to 760px), and we only want to run the function at that size. There is a JavaScript API called matchMedia, which allows you to test in JavaScript, exactly the same as you would in CSS. The obvious solution would be to use that and create a comparable test as you have in your media query.

However, it would still mean two places to...