I wrote a Medium post about mastering the DOM: medium.com/re-dom/master-the-dom-bc1a2a06089b
You can also check out my HTML5 Deck of Cards, which is open source: https://deck-of-cards.js.org it's quite easy to fiddle with: github.com/pakastin/deck-of-cards/tree/master/lib
Also check out a great book: http://eloquentjavascript.net
Happy JavaScripting!