100% solution for Count Div Task on Codility

CountDiv.js

function solution(A, B, K) {
  if (A == B) return A % K == 0 ? 1 : 0;
  if (K == 1) return B - A + 1;
  
  var count = 0;
  var start = 0;

  for (var i = A; i <= B; i++) {
    if (i % K == 0) {
      count++;
      start = i;
      break;
    }
  }

  for (; start + K <= B; start += K) {
    count++;
  }

  return count;
}