设置html的scrolltop,当设置 document.body.scrollTop = 0时，要如何还原回去？

html:

show div

hide div

function preventScroll(e){

//document.body.scrollTop=0;

e.preventDefault();

}

document.getElementById("showDivandFix").addEventListener("click",function(){

if(!document.getElementById("myDiv")){

var myDiv = document.createElement("div");

myDiv.id="myDiv";

myDiv.style.width="100px";

myDiv.style.height="100px";

myDiv.style.backgroundColor='#00ee00';

document.getElementById("myDivContainer").appendChild(myDiv);

}

document.getElementById("myDiv").style.display="block";

document.body.addEventListener("mousewheel",preventScroll,false);

},false);

document.getElementById("hideDivandremoveFix").addEventListener("click",function(){

document.getElementById("myDiv").style.display="none";

document.body.removeEventListener("mousewheel",preventScroll,false);

},false);

或者

jquery:

$(function(){

function preventScroll(e){

//document.body.scrollTop=0;

e.preventDefault();

}

$('button#showDivandFix').on("click",function(){

if($('#myDiv').length==0){

$('#myDivContainer').append("

}

$('#myDiv').show();

$('body').on("mousewheel",preventScroll);

});

$('button#hideDivandremoveFix').on("click",function(){

$('#myDiv').hide();

$('body').off("mousewheel",preventScroll);

});

});