var banners = new Array(
  "masthead_no_title_1.jpg",
  "masthead_no_title_2.jpg",
  "masthead_no_title_3.jpg",
  "masthead_no_title_4.jpg",
  "masthead_no_title_5.jpg",
  "masthead_no_title_6.jpg"
);

function getBanner() {
  var index = Math.floor(Math.random() * banners.length);
  return banners[index];
}

$(function(){
  var masthead = document.getElementById("interior-masthead");
  if (!masthead) return;
  if (masthead.className == "interior-masthead") {
    var banner = getBanner();
    masthead.style.backgroundImage = "url(/sites/all/themes/carnegiehq/images/" + banner + ")";
  }
});