How to reference an element passed by ID to function using getElementByID

[JJA]

I'm trying to use document.getEle mentByID inside a function where the
ID is passed as an argument. I get the same error ("Element has no
properties") on the same statement inside the commonCheck function
with either MS IE 6.0 or Mozilla Firefox 0.9. Comments below indicate
that if I hardcode an element ID I can avoid the error, but I
obviously want to parameterize it. Here are some snippets of my code:

-----snippet 1-------------------------------------------------------
<form method="POST" action="UserPro fileMaint.htm"
onSubmit="retur n validateTelnr ("txtPhone", "msgPhone", true);">
<p>&nbsp;</p>
<p>&nbsp;</p>
<table id="tblMain" border="0" width="100%">
<tr>
<td width="25%">&nb sp;</td>
<td width="25%">Pho ne</td>
<td width="25%"><in put type="text" name="txtPhone" id="txtPhone"
size="20"></td>
<td width="25%"><in put type="hidden" name="msgPhone"
id="msgPhone"> </td>
</tr>
-----snippet 2-------------------------------------------------------
function validateTelnr (vfld, // element to be validated
ifld, // id of element to receive
info/error msg
reqd) // true if required
{
var stat = commonCheck (vfld, ifld, reqd);
-----snippet 3-------------------------------------------------------
function commonCheck (vfld, // element to be validated
ifld, // id of element to receive
info/error msg
reqd) // true if required
{
if (!document.getE lementById)
return true; // not available on this browser - leave validation
to the server

var elem = document.getEle mentById(ifld); // this will fail on next
stmt
//var elem = document.getEle mentById("txtPh one"); //COMMENTED OUT:
this works
if (!elem.firstChi ld) //------> fails here with msg "elem has no
properties"
return true; // not available on this browser
if (elem.firstChil d.nodeType != node_text)
return true; // ifld is wrong type of node

if (emptyString.te st(vfld.value)) {
if (reqd) {
msg (ifld, "error", "ERROR: required");
vfld.focus();
return false;
}

[DGre]

JJA wrote:

Thank you! This example led me to fix the immediate problem. I had
tried passing the string to the function in double quotes and got a
syntax error. Your solution uses single quotes around the ID string
which I had not tried (I thought either was acceptable in Javascript
as long as they were not 'unbalanced"... ..

and now I am on to a new problem

If you submit your code as working examples rather than snippets, it is
much simpler to debug. With snippets, we can only user our eyes and
brains rather than debuggers and validators.

Cheers, DG