N.J. Stat. Ann. § 40:54-9

Immediately upon the establishment by any municipality of a free public library under this article, a board of trustees shall be formed to consist of from seven to nine members, one of whom shall be the mayor or other chief executive officer of the municipality, one of the local superintendents of schools, or in the event that there be no such official, the principal with power of supervision over the local school system, or in case such municipality shall have none of the school officials hereinbefore mentioned, then the president of the board of education, and from five to seven citizens to be appointed by the mayor or chief executive, at least four of who shall be residents of the municipality. The appointments shall be for terms of one, two, three, four and five years, respectively, as they may be selected by the mayor or other chief executive officer, and, except in cities, shall be made with the consent of the governing body. Whenever a board is expanded to include a sixth or seventh citizen, the additional members shall serve terms of five years. The mayor or other chief executive officer and the superintendent of schools or the principal, as the case may be, serving as a member of the board, may, respectively, appoint an alternate to act in his place and stead with authority to attend all meetings of the board and, in his absence, to vote on all questions before the board.