Javascript startsWith() help

Javascript startsWith() help

This code is not working. I don't know much about Javascript but I am trying. The startsWith() function is what I added to the code and it killed everything. What am I doing wrong here?
  1. var idToShow = location.pathname.split("/")[1];

  3. if (idToShow == "index") {
  4. $("#home").show();
  5. }
  6. else if (idToShow.startsWith("_webapp")) {
  7. $("#district").show();
  8. }
There is obviously more to this but hopefully you will be able to see what is wrong here.
When ran it completely kills my code.

Thanks!
Austin