获得域用户名称的javascript脚本

<script language="javascript" type ="text/javascript">
function setuser(tUsername)
{ 
    var wshNetwork=new ActiveXObject("WScript.Network");
    var tUser=document.getElementById(tUsername);
    alert(tUsername)
   
    alert(tUser.value);

    if(tUser!= "undefine")
    {
        tUser.value=wshNetwork.UserName;
        alert(tUser.value);
    }
}
</script>