Ask HN: Resources for Updating JavaScript Skills?

The last time I did any heavy lifting with Javascript, jQuery was mandatory and Backbone and Mustache were hot. (So, yeah, only about 5 years ago.) But with a new side project requiring a modern front-end, it's time to get up to speed on the modern ecosystem.

A grasp of the absolute basics should be all I need to be able to research and learn the rest as the need comes up. What are some good practical introductory resources on the following topics that are aimed at a reasonably experienced Javascript developer and that won't take more than an hour or so each to grok?

1) modern javascript package management

2) React

3) ES6