让html元素随浏览器的大小自适应垂直居中的实现方法

function divMiddle(){
	var dairyBox = document.getElementById('dairyBox');
	var divHeight = dairyBox.offsetHeight;
	var bodyHeight = document.body.offsetHeight;
	if(bodyHeight > divHeight){
		var endHeight = parseInt(bodyHeight - divHeight)/2;
		dairyBox.style.marginTop = endHeight + "px";
	}else{
		dairyBox.style.marginTop = 0;
		dairyBox.style.top = 0;
	}
}
            
if(document.all){
	window.attachEvent('onload',divMiddle);
}else{
	window.addEventListener('load',divMiddle,false);
}
             
var resizeTimer = null;
window.onresize = function(){
	resizeTimer = resizeTimer?null:setTimeout(divMiddle,0);
}