title: How to detect when an iframe has already been loaded
body: <p>It seems that <code>$('#someIframe').load(function(){...})</code> won't fire if it is attached after the iframe has finished loading. Is that correct? </p>
  
  <p>What I'd really like is to have a function that is always called once when or after an iframe has loaded. To make this clearer, here are two cases:</p>
  
  <ul>
  <li><strong>Iframe hasn't loaded yet</strong>: run a callback function once it loads.</li>
  <li><strong>Iframe has already loaded</strong>: run the callback immediately.</li>
  </ul>
  
  <p>How can I do this?</p>