Recommended and mentioned products
RegExr.com is an online tool to learn, build, and test Regular Expressions.
Regexr.com - getting to grips with the basics of Regular Expressions would be a lot harder without somewhere to sketch ideas out and see them work.
Open source API documentation browser with instant fuzzy search, offline mode, keyboard shortcuts, and more
Devdocs.io - the breadth of easily accessible info here is incredible!.