Moi aussi :

// Initial state
var scrollPos = 0;
// adding scroll event
window.addEventListener('scroll', function(){ scrolling() });

// the function : compares the "new" scrolling state with the previous
// (this allows detecting either "up" or "down" scrolling)
// then saves the new in the $previous for the next iteration.

function scrolling() {
    if ((document.body.getBoundingClientRect()).top > scrollPos) {
        console.log('scrolling DOWN');
    } else {
        console.log('scrolling UP');
    }
    scrollPos = (document.body.getBoundingClientRect()).top;
}

Trop bien, merci KraZhtest !