var resizeBg = function() {
var w = self.innerWidth || document.documentElement.clientWidth;
var h = self.innerHeight || document.documentElement.clientHeight;
if (bgimg.width !== w) {
bgimg.parentNode.style.left = '0';
bgimg.parentNode.style.top = '0';
bgimg.height = (w / bgimg.width) * bgimg.height;
bgimg.width = w;
}
if (bgimg.height <h) {
bgimg.width = (h / bgimg.height) * bgimg.width;
bgimg.height = h;
bgimg.parentNode.style.left = '-' + ((bgimg.width - w) / 2) + 'px';
}
else if (bgimg.height> h) {
bgimg.parentNode.style.top = '-' + ((bgimg.height - h) / 2) + 'px';
}
}