How to set control visible in Java script

function displayRow1()
{
if (document.form1.ddlstatus.value == "Select")
{
document.all.item('trdor').style.display = "none";
}
if (document.form1.ddlstatus.value == "Working")
{
document.all.item('trdor').style.display = "none";
}
if (document.form1.ddlstatus.value == "Resigned")
{
document.all.item('trdor').style.display = "";
document.form1.txtDOR.focus();
document.form1.txtDOR.select();
}
}