[malft]

Several of the examples have an extra lambda like this. What does it do?

const toArray = (() => Array.from ? Array.from : obj => [].slice.call(obj) )();

[benjamindc]

It's an IFFE (Immediately-Invoked Function Expression). The goal is to perform the feature test (the availability of Array.from in this case) just once instead of for every function call.