The following series by Alexander Zlatkov provide a deep understanding of the core elements of the JavaScript language. The material is well-researched and easy-to-follow.
I highly advise you to read these articles if you’re interested in learning more about JavaScript, particularly on what is going on under the hood.
- Part 1: How JavaScript works: an overview of the engine, the runtime, and the call stack
- Part 2: How JavaScript works: inside the V8 engine + 5 tips on how to write optimized code
- Part 3: How JavaScript works: memory management + how to handle 4 common memory leaks
- Part 4: How JavaScript works: Event loop and the rise of Async programming + 5 ways to better coding with async/await