How to run KA JavaScript project code in an HTML file on GitHub?

Can you clarify where you want to run your code? If you're looking to share your code on Khan Academy and run it there, you can create a new webpage (New webpage) and paste the entire contents of that index.html file inside. KA's Oh Noes might complain about your script tags—that's because of some deprecated JS formatting. The trick to getting it to work is to add an empty type attribute to your opening script tag:

<script type>
  // your Javascript
</script>

If you're trying to run your code on GitHub itself, there are a few things you should know. GitHub is just a place to store code files—it's not a code playground where you can run and test code with a click of a button like KA. That's not its main purpose. That being said, since your code is a static webpage (just plain HTML/CSS/JS), GitHub has something called GitHub Pages which is basically a free static web hosting service. When you activate it on a repo with static webpage files, it gives you a publicly accessible URL and your webpages become a publicly accessibly website on the internet. If you'd like to do that, it's very easy. Just active GitHub Pages in your repository settings. Here's the official guide:
https://docs.github.com/en/pages/getting-started-with-github-pages/creating-a-github-pages-site#creating-your-site

If you're looking for a similar code playground experience outside of Khan Academy, try out CodePen. You can run HTML/CSS/JS and it fully supports modern web standards with a lot more features too.

Happy coding.

Welp, I made a reply to this thread several days ago that was pendin' approval. It had links pointin' to a couple parts in the program and repository on GitHub to show what I was talkin' about, but I guess the dumbheads runnin' this dumb website don't want that. So, ya know what. Forget it. I may or may not eventually figure it out someday. I'm not gonna bother tryin' to retype it all (not to mention the fact I can't even remember exactly what I wrote to begin with).

For anyone who is readin' this thread in the future tryin' to do the same or somethin' similar to what I was doin' or hopin' to find this thread helpful: I apologize that this thread was zero help. It's not my fault that programmers have to make things so complicated, that people on this website are unhelpful, and that the site has to be such a pain in the... yeah, I think ya might know what word I was about to say (and can't for "reasons").

Good night. And good grief.

Sincerely,

A programmer who hopes to become a good programmer someday

P.S. Now I'm beginnin' to remember why I ditched this site a while back in the first place...

So sorry to hear that, I too have struggled with asking for help here in the past and I totally get your frustration.

Did you catch my earlier reply to your original post above? On my end it seems visible. Please let me know if you did, and if you have any follow-up questions just let me know, I'd be more than happy to answer them.

Adding links here can be tricky, so try to keep your links local to Khan Academy to be safe. Sometimes posts get automatically hidden even if you post a perfectly harmless link leading off the KA domain. It's annoying, I know, but important for safety reasons.

Sincerely, 
A fellow programmer who believe you can become an awesome programmer way sooner than you think :)