Checking If Span Object(s) Exist

We have a JSP website intended for viewing with IE 5 (and above)
On a certain jsp page, there are few span objects
(<SPAN ID="name">text</SPAN>), which are created dynamically.

The spans share the same ID, so we are able to reference them as an
array, in the javascript code :
for example:

<SPAN ID="wow">lala</SPAN>
<SPAN ID="wow")kaka</SPAN>

in the JS code:

wow[0].innerHTML = "fafa";
wow[1].innerHTML = "zaza";

It may occur, since these spans are created dynamically by the JSP
page, that on a certain instance of the page, no spans are created.

My question is - how do we know, in the JS code, that no spans of ID
'wow' exist?
We tried several ways:

if (!wow) alert('no wow'); // If there were no spans, this gives a
js error

tried a few other methods which i cant recall of now..
I know of a workaround - to add a 'dummy' span with the 'wow' ID , but
I prefer to know if there is a better way to deal with this.