js返回页面顶部

 
 

http://blog.csdn.net/zjl_wzw/article/details/4384506

//////////////////////////////////////////////

//<![CDATA[

var goto_top_type = -1;

var goto_top_itv = 0;

 

function goto_top_timer()

{

var y = goto_top_type == 1 ? document.documentElement.scrollTop : document.body.scrollTop;

var moveby = 15;

 

y -= Math.ceil(y * moveby / 100);

if (y < 0) {

y = 0;

}

 

if (goto_top_type == 1) {

document.documentElement.scrollTop = y;

}

else {

document.body.scrollTop = y;

}

 

if (y == 0) {

clearInterval(goto_top_itv);

goto_top_itv = 0;

}

}

 

function goto_top()

{

if (goto_top_itv == 0) {

if (document.documentElement && document.documentElement.scrollTop) {

goto_top_type = 1;

}

else if (document.body && document.body.scrollTop) {

goto_top_type = 2;

}

else {

goto_top_type = 0;

}

 

if (goto_top_type > 0) {

goto_top_itv = setInterval('goto_top_timer()', 50);

}

}

}

//]]>

<a href="javascript:void(0)" onclick="goto_top()">返回页顶</a>

 

 

/////////////////////////////
http://tommyhu.cn/post/1230/

<script>

lastScrollY=0;

function heartBeat(){

var diffY;

if (document.documentElement && document.documentElement.scrollTop)

diffY = document.documentElement.scrollTop;

else if (document.body)

diffY = document.body.scrollTop

else

{/*Netscape stuff*/}

percent=.1*(diffY-lastScrollY);

if(percent>0)percent=Math.ceil(percent);

else percent=Math.floor(percent);

document.getElementById("full").style.top=parseInt(document.getElementById("full").style.top)+percent+"px";

lastScrollY=lastScrollY+percent;

if(diffY == 0){document.getElementById("full").style.display = "none"}

else{document.getElementById("full").style.display = "block"}

}

suspendcode="<div id=\"full\" style='display:none; width:20px; height:90px; POSITION:absolute; left:50%; top:500px; margin-left:460px;  z-index:100; text-align:center;'><a href='#'><img src='http://tommyhu.cn/images/others/gototop.gif' border=0 alt='返回顶部'></a></div>"

document.write(suspendcode);

window.setInterval("heartBeat()",1);

</script>