To add some more advice combining the suggestions of @kingjeffrey and @CMS: You can use loop where it is available and fall back on kingjeffrey's event handler when it isn't. There's a good reason why you want to use loop and not write your own event handler: As discussed in the Mozilla bug report, while loop currently doesn't loop seamlessly (without a gap) in any browser I know of, it's certainly possible and likely to become standard in the future. Your own event handler will never be seamless in any browser (since it has to pump around through the JavaScript event loop). Therefore, it's best to use loop where possible instead of writing your own event. As CMS pointed out in a comment on Anurag's answer, you can detect support for loop by querying the loop variable -- if it is supported it will be a boolean (false), otherwise it will be undefined, as it currently is in Firefox.
Putting these together:
myAudio = new Audio('someSound.ogg');
if (typeof myAudio.loop == 'boolean')
{
myAudio.loop = true;
}
else
{
myAudio.addEventListener('ended', function() {
this.currentTime = 0;
this.play();
}, false);
}
myAudio.play();