Adding event listener to audio HTML5 tag in javascript

Hi I'm creating a new audio tag element in Javascript this is the code:

var audio = document.createElement("audio");
audio.setAttribute("id","myid");
audio.setAttribute("autoplay","autoplay");
document.body.appendChild(audio);

before appending it to the body, I'd like to place an onended event handler, I tried something like this:

audio.onended = foo;

where foo is something like: function foo(){alert('Hola')}

and

audio.setAttribute("onended","foo()");

in both case it didn't work. In the first case the audio tag is appended without any onended event handler; while in the second case the audio tag is appended, the onended event is on the attributes but it does not fire.

does someone have any idea?

thanks in advance.

-z-