Instead of making an alert modal popup coming up when the submit button was clicked, however, I kept getting a pop-up right next to the select list field that said "Please select an item in the list."
Strangely, when I would try to use the web inspector to inspect the pop-up element, the element would disappear as soon as I clicked the inspect tool in the dev tools.
Finally, I looked at the html. There it was:
<select id="s-state" required>
As soon as I removed that, the js alert started working. Of course, if I had just kept watching the tutorial, it turns out that Chellman had the user add the "required" to the select list in the the index.html file. In this case, though, the beginning code probably should not have included the "required." Nevertheless, I eventually figured it out and learned something about an HTML5 tag I did not know about.