Codility: PassingCars Solution

1function solution(A) {
2  let count = 0
3  const prefixZeros = A.map(a => (count += a === 0 ? 1 : 0))
4  const res = prefixZeros.reduce(
5    (acc, el, i) => (acc += A[i] === 1 ? el : 0),
6    0
7  )
8  return res > 1e9 ? -1 : res
9}