title: Add an OnClick handler with jQuery only once - even if called again
body: <p>If I assign a handler to the OnClick event of an element twice, the handler will be executed twice.  But I want to change this so even if I assign it twice, the handler will only execute one time.</p>
  
  <p>Nonsensical example to demonstrate issue:</p>
  
  <pre><code>$('.button').click(
      function(){
         alert('here');
  });
  $('.button').click(
      function(){
         alert('here');
  });
  </code></pre>
  
  <p>So I've added the handler twice.  Now when I click an element with that class, I'd get two alert boxes.</p>
  
  <p>The question is, how do I restrict it so I would only get one alert box?</p>