One thing if you could touch upon is the mutlithreaded nature, or lack thereof, of JavaScript.

Some questions that Google searches have not explained fully enough includee:

How the JavaScript engine works in the browser context. For example, what happens when an XMLHttpRequest completes and calls the onreadystatechange function and there’s another event being processed. Does the onreadystatechange block, or are they both running?

Do you need to worry about multiple threads updating JavaScript variables?

Are all JavaScript implementations single threaded?

Is there a global lock much like Python?