title: jquery determine amount of overlap between 2 divs
body: <p>I have two divs (rectangles) that overlap each other.  How do I determine the amount of intersection/overlap between the two divs in javascript?</p>
  
  <p>I realize I'll get the dimensions for each rectangle:<br />
  offset.top, offset.left, elt.offsetWidth, elt.offsetHeight</p>
  
  <p>But from there I'm unsure how to determine the amount of overlap.</p>