The article was quite detailed and explained the concepts very well. I liked the example which you used for explaining problems created when we use var instead of let for defining variables.
I had learnt the concept of call stack/event loop quite easily before, when it was explained using a diagram like the one used in node.js dev docs:- nodejs.dev/learn/the-nodejs-event-loop
Such diagrams would be something which you can consider using in upcoming articles for better explanation of such concepts. That's the only recommendation from my end. Keep up the great work👍🏽