帮我把下面的代码改成可以兼容火狐

Question

<SCRIPT language=javascript>
var iShowMenu = -1;

function showLayer(sid)
{
whichEl = eval("Layer" + sid);
if (whichEl.style.display == "none")
{
if (iShowMenu != -1)
{
eval("Layer" + iShowMenu + ".style.display=\"none\";");
}

eval("Layer" + sid + ".style.display=\"\";");
iShowMenu = sid;
}
else
{
eval("Layer" + sid + ".style.display=\"none\";");
iShowMenu = -1;

}
}
</SCRIPT>

Answer 1

<SCRIPT language=javascript>
    var iShowMenu = -1;
    
    function showLayer(sid)
    {        
        whichEl = document.getElementById("Layer" + sid);
        if (whichEl.style.display == "none")
        {            
            if (iShowMenu != -1)
            {
               document.getElementById("Layer" + iShowMenu + ").style.display="none";
            }
            
           whichEl.style.display = "";
            iShowMenu = sid;
        }
        else
        {
            whichEl.style.display = "none";
            iShowMenu = -1;
            
        }
    }
</SCRIPT>

Answer 2

document.getElementById("Layer" + iShowMenu + ").style.display="none";
==>
document.getElementById("Layer" + iShowMenu ).style.display="none";