Cassidoo's Interview question of the week

cassidoo-1-august-2022.js

/* 
 * Given an integer n, count the total number of 1 digits appearing in all non-negative integers less than or equal to n. 
 *
 * > numberOfOnes(14)
 * > 7 // 1, 10, 11, 12, 13, 14
 *
 */
 
 function numberOfOnes(n) {
  return [...Array(n + 1).keys()].reduce(
    (ones, current) => ones + (current.toString().split("1").length - 1)
  );
}