js将对象居中函数

//将对象居中显示function movemiddle(obj){	if(!obj) return ;		obj.style.display = "block";		var screenwidth = document.documentelement.clientwidth;	var screenheight = document.documentelement.clientheight;	var scrollposy = 0;	var scrollposx = 0	if(typeof window.pageyoffset != 'undefined'){		scrollposy = window.pageyoffset;	}else if(typeof document.documentelement != 'undefined'){		scrollposy = document.documentelement.scrolltop;	}	if(typeof window.pagexoffset != 'undefined'){		scrollposx = window.pagexoffset;	}else if(typeof document.documentelement != 'undefined'){		scrollposx = document.documentelement.scrollleft ;	}		var divwidth = obj.offsetwidth;	var divheight = obj.offsetheight;	var divleft = parseint((screenwidth - divwidth) / 2);	var divtop = parseint((screenheight - divheight) / 2);	divtop = divheight > screenheight ? 10 : divtop + scrollposy;	divleft = divwidth > screenwidth ? 10 : divleft + scrollposx;	obj.style.left = divleft + "px";	obj.style.top = divtop + "px";	}