The JavaScript is very simple and looks like this:

<script type="text/javascript">

function buttonClick(){
  
  var elem = document.getElementById('selection');
  
  elem.innerHTML = document.getElementById('year').value;
} 

</script> 

You can see that we grab the element with the ID of selection and write the value of the year to it. You will, I am sure, wish to produce something a little more sophisticated than this! Now we have the basics, the second example is a bit more complex. In this example, we will be passing messages directly between server (R) and client (JavaScript).