双击网页向上滚动

var currentpos,timer; 
function initialize() { 
    timer=setInterval("scrollwindow()",10);
} 
function sc(){
    clearInterval(timer); 
}
function scrollwindow(){ 
	currentpos=document.body.scrollTop; 
	window.scroll(0,++currentpos); 
	if (currentpos != document.body.scrollTop) 
	sc();
} 
document.onmousedown=sc;
document.ondblclick=initialize;