codility.js

// task1
function solution(A) {
  var pos = 0;
  var len = A[pos] !== -1 ? 1 : 0;
  // if -1 last node
  while(A[pos] !== -1 && A[pos] !== undefined){
    len++;
    pos = A[pos];
  }
  return len;
}
console.log(solution([-1, -1, -1, 3, 2]));//0
console.log(solution([1, 4, -1, 3, 2])); // 4
console.log(solution([1, 4, 3, -1, 2])); // 5
console.log(solution([1, 4, 3])); // 3