jsMediaQuery.js

function myFunction(x) {
    if (x.matches) { // If media query matches
        document.body.style.backgroundColor = "yellow";
        console.log('one time only');
    } else {
        document.body.style.backgroundColor = "pink";
        console.log('pink');
    }
}

var x = window.matchMedia("(max-width: 700px)")
myFunction(x) // Call listener function at run time
x.addListener(myFunction) // Attach listener function on state changes