I did a ton of JavaScript development up till about 2010 (ArcIMS HTML viewer), and then took a detour through other career options before coming full circle, and I'm a bit rusty. What skills do I need to get up to speed with version 4 of the ArcGIS API for JavaScript, particularly with the forthcoming Experience Builder? I like to learn by tinkering, but I also try to do some self-study to round out my skill set.
In particular, JavaScript looks a lot different now than 2010. I am wondering what version of JavaScript is best to learn? I'm NOT talking about the Esri API version, but rather the version of ECMAScript, i.e.: JavaScript itself, that is used by version 4 of the API. (If this question is still unclear, see here.)
Asking around at the user conference, I also heard various things, like TypeScript, Node.js, JSX, & Sass. Regarding JSX, I got conflicting answers about whether knowing the underlying React technology is necessary.
thanks!