Without the unary operator one cannot enter negative numbers without introducing additional complexity in the lexer/parser. For example: var m1 = -1; The "-1" can be thought of as a negative constant, but if the lexer assumes that, so you get problems with: var m2 = 2-1; Which would be lexed as number(2) number(-1) and a syntax error, as opposed to the correct number(2) operator(-) number(1). Can we conclude that there are therefore no negative numeric constants?