Ask HN: How to learn how to use JavaScript effectively?

I learned Javascript as a general-purpose programming language some time ago, but I never actually learned how to make it interact with websites.

I want to learn how to use my browser's developer tools and how to use JS to manipulate the websites I browse (e.g. by submitting keystrokes). I also want to learn how to use Javascript on the websites I own to manipulate the DOM and deliver content.

I assume the web is full of resources on these matters, but it's hard to find good ones. Where should I go to learn about these topics? Which resources teach how to make the most of applying JS? I want to learn how to be really productive with JS --- where should I go?