map, filter, reduce in action

dogHuman.js

const agesOneArr = [5, 2, 4, 1, 15, 8, 3];
const agesTwoArr = [16, 6, 10, 5, 6, 1, 4];

const calcAverageHumanAge = function (ages) {
  const dogToHumanYrs = ages.map((age, i) =>
    age <= 2 ? 2 * age : 16 + age * 4
  );
  const eighteenOrOlder = dogToHumanYrs.filter(age => age > 18);
  console.log(eighteenOrOlder);

  const averageAge = eighteenOrOlder.reduce(
    (a, b) => a + b / eighteenOrOlder.length,
    0
  );

  return averageAge;
};

// method chaining

console.log(calcAverageHumanAge(agesOneArr));
console.log(calcAverageHumanAge(agesTwoArr));

console.log(`----------------------`);

const calcAverageHumanAgeSlim = function (ages) {
  const dogToHumanYrs = ages
    .map((age, i) => (age <= 2 ? 2 * age : 16 + age * 4))
    .filter(age => age > 18)
    .reduce((acc, age, i, arr) => acc + age / arr.length, 0);

  return dogToHumanYrs;
};

console.log(calcAverageHumanAgeSlim(agesOneArr));
console.log(calcAverageHumanAgeSlim(agesTwoArr));