Write a JavaScript program to group the elements of an array based on the given function and returns the count of elements in each group

const countBy = (arr, fn) =>
  arr.map(typeof fn === 'function' ? fn : val => val[fn]).reduce((acc, val, i) => {
    acc[val] = (acc[val] || 0) + 1;
    return acc;
  }, {});
console.log(countBy([6, 10, 100, 10], Math.sqrt));
console.log(countBy([6.1, 4.2, 6.3], Math.floor));
console.log(countBy(['one', 'two', 'three'], 'length'));