For trick number 5, forEach seems like a fine approach, but stylistically I'm more pulled towards Reduce since Javascript doesn't have a maxBy or equivalent.

const array = ["Apple", "Pine-apple", "Banana", "Jack-fruit"];

const longest = array.reduce((longest, current) => {
  if (longest.length < current.length) {
    return current;
  }

  return longest;
});

console.log(longest); // Pine-apple

Ternary version looks a lot cleaner, but are notoriously harder to read.

const array = ["Apple", "Pine-apple", "Banana", "Jack-fruit"];

const longest = array.reduce((longest, current) =>
  current.length > longest.length ? current : longest
);

console.log(longest); // Pine-apple