Errata

Below are some known errata in the Mastering Functional Programming with JavaScript course by Packt Publishing.

Volume 1 (Learn to Write Functional JavaScript)

Video 1.8

The every and some functions don't apply the predicate function over the last element in the arrays being tested. Thanks to for @invegat for pointing this and providing a fix. The videos will be updated soon as well.

Here is the every function fix

  function every(predicate, list = []) {
    if (list.length) {
      const [item, ...remaining] = list
      return predicate(item) ? every(predicate, remaining) : false
    }
    return true
  }

And here is the updated some function

function some(predicate, list = []) {
  if (list.length) {
    const [item, ...remaining] = list
    return predicate(item) ? true : some(predicate, remaining)
  }
  return false
}