This is for people who have never written JavaScript and want a web page that reacts when someone clicks, types or submits. You will write JavaScript that runs in your browser, change the page with it, and read your own errors instead of pasting code you don't understand. If you skip the basics and copy snippets until something works, you will be stuck the first time the console turns red, and it will turn red.
This is for people who can already make a page react with JavaScript and now need code that survives real projects: Node and npm, modules, classes, real data, waiting for APIs, and tests. You will set up projects that install the same way on every machine, split code into files other people can read, handle JSON and dates without losing data or a day, and prove your code works before a customer finds out it doesn't. If you skip this level, your code works on your machine with your sample data, and breaks the first time the data changes.
This is for people who already write Node and browser JavaScript with modules, async/await and tests, and now need code that keeps working under real load. You will learn how closures and this really behave, how the event loop orders your code, how to run, limit and cancel async work, how to process data that doesn't fit in memory, how to catch type bugs without switching to TypeScript, and how to ship a package and find slow code and memory leaks. If you skip this level, your code passes every test and still falls over the first week it runs in production.