I hate to be the one to tell you this, but you really need to learn all three of those (HTML, CSS, and JS), because they all work together.
HTML is what you use to create the page and display the text and such.
CSS is what you use to make the HTML look worth a crap.
JS is what you use to manipulate the text (and such) on the page after it has loaded.
If you only learned HTML, it would look like crap and nothing would happen. You could only print out plain-looking text one time. (No game.)
If you only learned CSS, you'd have no HTML to stylize with your CSS. So, that would be a waste of time.
If you only learned JS, you'd have no HTML to manipulate. (NOTE: You could use your JS skills in NodeJS or Deno apps, but each of those apps would need to be downloaded and ran as stand-alone apps. They would be severely less universally accessible than a website (made with HTML, CSS, and JS). Plus, you couldn't post the apps on this site.)
The good news is that you most probably already know much more HTML, CSS, and JS than you realize. I opine this because you've been using Quest for so long, and Quest is basically a glorified browser that only loads Quest games. It displays HTML, and we use CSS and JS to manipulate that HTML in our games.
HTML and CSS are relatively simple, I would suggest starting there. You will get JS better once you have a start in them.
There are online tutorials you might want to look at:
But yes, I would get the book on JS.
When I try to do
JS.console.log ("Welcome!"), nothing happens. But when I do
JS.document.write ("Welcome!"), it prints "Welcome!", but absolutely nothing else! Can someone explain this to me?
JS.console.log ("Welcome!") prints a message to the developer console. Press F12 (in most browsers) and select the Console tab, and you should see it.