Really simple jquery parallax background

simple-parallax.js

var body;
var backgroundPosition;
var scrollPosition;
var parallaxAmount = 6;

$(document).ready(function () {
  body = $('body');
});

$(window).scroll(function () {
  scrollPosition = $(window).scrollTop();
  bkgPos = -(Math.floor(scrollPosition/parallaxAmount));
  body.css('background-position', 'center ' + backgroundPosition + 'px');
});