challenge-18.js

// Convert array to object with counter

// Write a function that takes an array of numbers as argument
// Convert the array to an object
// It should have a key for each unique value of the array
// The corresponding object value should be the number of times the key occurs within the array

function myFunction(a) {
  return a.reduce((acc, cur) => ({ ...acc, [cur]: acc[cur] + 1 || 1 }), {});
}

console.log(myFunction([1, 2, 2, 3])); // Expected: {1:1,2:2,3:1}
console.log(myFunction([9, 9, 9, 99])); // Expected: {9:3,99:1}
console.log(myFunction([4, 3, 2, 1])); // Expected: {1:1,2:1,3:1,4:1}