Speaking of Sandi Metz, here’s a 30-minute talk she did at RailsConf 2015. It’s the kind of developer talk that’ll stretch your mind. I love this core idea she kept iterating on:
I don’t want to write a condition; I just want to send a message to an object.
Also this very practical tidbit:
Inheritance is for specialization. It is not for sharing code.
undefined is extremely commonplace. It’s one of the reasons TypeScript was such a big deal when it was announced, although it’s a mixed bag to say the least.