New Jersey Statutes Title 40A. Municipalities and Counties 40A § 14-129

In any municipality wherein Title 11 (Civil Service)  1 of the Revised Statutes is not in effect, and except in cities of the first and second class, a promotion of any member or officer of the police department or force to a superior position shall be made from the membership of such department or force. Due consideration shall be given to the member or officer so proposed for the promotion, to the length and merit of his service and preference shall be given according to seniority in service.

No person shall be eligible for promotion to be a superior officer unless he shall have previously served as a patrolman in such department or force.