Why unary operator before exponentiation expression in JavaScript cannot be evaluated? [duplicate]

I noticed that expression like “-3**2” is considered ambiguous in JavaScript. For example, in Chrome, the error is thrown as “Uncaught SyntaxError: Unary operator used immediately before exponentiation expression. Parenthesis must be used to disambiguate operator precedence.”

From the perspective of compiler (specifically, parser I think) or syntax designer, why this input is not allowed? If I were the designer of the compiler, maybe I would just assign a higher precedence to unary operator, or the other way, instead of throw an error.