[5kyu] Product of consecutive Fib numbers

[F(n), F(n+1), true] or {F(n), F(n+1), 1} or (F(n), F(n+1), True)

[F(n), F(n+1), false] or {F(n), F(n+1), 0} or (F(n), F(n+1), False)

productFib(714) # should return (21, 34, true), 
                # since F(8) = 21, F(9) = 34 and 714 = 21 * 34

productFib(800) # should return (34, 55, false), 
                # since F(8) = 21, F(9) = 34, F(10) = 55 and 21 * 34 < 800 < 34 * 55
-----
productFib(714) # should return [21, 34, true], 
productFib(800) # should return [34, 55, false], 
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productFib(714) # should return {21, 34, 1}, 
productFib(800) # should return {34, 55, 0},        
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productFib(714) # should return {21, 34, true}, 
productFib(800) # should return {34, 55, false},

export const productFib = (prod:number): [number,number,boolean] => {
  let front = 0,
      back = 1
  while (front * back < prod) {
    back += front
    front = back - front
  }
  return [front, back, front * back === prod]
}