This however is not beginner level. I’d say it’s intermediate but to understand what you’re doing you will need a bit of experience with basics. So I’m going to link a few different things, and it’s up to you if you’re willing to go that way.
For the code from reply 8, understanding of the HTML block model/DOM is needed. Remember the stacking wooden figurines comparison I made in the other thread? Exactly like that. The
document.getElementById call searches for an element from the html added to the template with the
id attribute set to that value.
W3Schools has a decent tutorial to get started with HTML. To understand what is going on here/things that might be useful for understanding other Node-RED topics too.
If you follow that until they start talking about
<canvas> it will cover most you’ll might encounter.