A simple parallax effect on scroll

plax

var Plax = function() {
    var plax = document.querySelectorAll('.plax');

    for (var i=0; i<plax.length; i++) {
        plax[i].style.position = 'fixed';
    }

    document.onscroll = function() {
        for (var i=0; i<plax.length; i++) {
            plax[i].style.top = (-plax[0].getAttribute('data-plax') * document.body.scrollTop) + 'px';
        }
    }
}