Overview
A short chapter video is here....
Using labs (or playgrounds) is a great way to learn, doing experiments...
JavaScript is an experimentation friendly language (maybe the most so).
It's "loose" (not part of a project) code so generally that it's "throw-a-way" (with the occasional snippet capture and archive).
Lab Editor
This is coder's choice. Pick the editor(s) that you find the most user-friendly.
Some ideas:
JavaScript Guide
(Chapter 401 - LabIntro)