title: How to diagnose what feature that is failing for a particular javascript?
body: <p>I'd like to leverage a (to me) complicated Javascript, <a href="https://github.com/codecomputerlove/PhotoSwipe" rel="nofollow">Photoswipe</a>. The author is clear that they don't support IE 7, and although the demo site does function to some degree in IE 7, the instance my team built does not. </p>
  
  <p>Rather than try to modify the script, I'd like to use something like <a href="http://yepnopejs.com/" rel="nofollow">Yep/Nope</a> to detect which Javascript feature is failing and provide a simpler alternate gallery that I know works well in old browsers. I'm trying to avoid user-agent sniffing.</p>
  
  <p>Is there a tool or method available to sort out what to feature-detect against in a script that you don't know the ins-outs of personally?</p>