title: How to discover broken html/javascript in IE11?
body: <p>I'm trying to use the polyfill for making server-side Blazor work in IE11 here:
  <a href="https://github.com/Daddoon/Blazor.Polyfill" rel="nofollow noreferrer">https://github.com/Daddoon/Blazor.Polyfill</a></p>
  
  <p>My sample Blazor app just freezes.  I don't see any messages in the debug window.  I'm assuming that the component library I have created is at fault.  I realize that the polyfill is specific to Blazor infrastructure.  An example is here and it should be loading the polyfill just mentioned if you use IE11:  <a href="https://blazorfabric.azurewebsites.net/" rel="nofollow noreferrer">https://blazorfabric.azurewebsites.net/</a></p>
  
  <p>However, I have no idea how to go about discovering which API or which html element I have used is not allowed on IE11.  Is there a tool that scans code to find potential issues with IE11?  Is there some giant polyfill that could be added (temporarily) that will most likely make it work?</p>
  
  <p><strong>Edit 1/22/20</strong>
  So through pure guessing (pick a random thing and see if it isn't supported on IE11 via caniuse.com), I discovered that custom css properties don't work on IE11.  The polyfill that fixes this is: <a href="https://github.com/nuxodin/ie11CustomProperties" rel="nofollow noreferrer">https://github.com/nuxodin/ie11CustomProperties</a></p>
  
  <p>The page now loads and sort of works.  I can't really get the developer console to do much, but the page does respond and it looks (mostly) good.</p>
  
  <p>This still doesn't answer the question.  If the debugger doesn't throw an exception on a line of code, it's not clear what to do.  </p>