The nitty gritty details about script loading order: inline scripts vs external scripts, synchronous loaded vs async loaded scripts, deferred scripts, and adding scripts programmatically later to the DOM (there be dragons)
the difference between ES5 and ES6 and how to transpile
ES5 fallback scripts with nomodule and ES6 module-based scripts.
automated polyfills: what can polyfill.io do for you? how to use corejs together with babel to automatically add needed polyfills?
bundling: what is the difference between a webApplication bundle and a library bundle? How to exclude dependecies in the latter case.
package.json: differences between dependencies, devDependencies, peerDependencies
module formats in js: commonJS vs UMD vs AMD vs ES6
learning why the IIFE pattern is relevant
Events in the UI: bubbling vs capturing phase and why it matters sometimes
Why e.stopPropagation breaks other components, and e.preventDefault is the way to go.
how the css property display: contents allows you to include wrappers for elements without destroying layouts that rely on direct-parent-child: like the flexbox
how the stacking-context allows you to never again need the z-index arms race with z-index: 999999; and the likes.
nomoduleand ES6 module-based scripts.e.stopPropagationbreaks other components, ande.preventDefaultis the way to go.display: contentsallows you to include wrappers for elements without destroying layouts that rely on direct-parent-child: like the flexboxz-indexarms race withz-index: 999999;and the likes.