title: Determine what triggered focus event?
body: <p>I need to determine what caused a focus event.</p>
  
  <p>Ideally, I want to differentiate between a click, a tab/keyboard input, and a manual (via code) trigger.</p>
  
  <p>How can I do this?</p>
  
  <p>I'm looking at the event object, but I'm not seeing anything too useful.</p>