Prototype - click event on an image

Question

I am trying to respond to a click event on a image like so. Why isn't this working?

$$('refresh').each(function(element) {     
    element.observe('click', respond); 
}) 

function respond(event) {     
    alert("hello"); 
} 

<img src="images/refresh.jpg" id="refresh" />

Answer 1

Updated

See DEMO

Use $('refresh') instead of $$('refresh'), or $$('#refresh'). But second variant returns array anyway. See links: $ and $$. And I don't understand how do you bind event handler.

All code:

<img id="refresh" src="images/refresh.jpg" />

<script>
  $$('#refresh').each(function (element) {     
    Event.observe(element, 'click', respond); 
  });

  function respond (event) {
    alert("hello"); 
  }
</script>