The result of an expression with an arithmetic operator /, *, %, ++, --, -, +=, -=, *=, /=, %=, + or unary operator +, -
when at least one operand is Object or Undefined will be always a NaN (Not a Number).
x = [1, 2]; var y = x / 4; //Noncompliant
Date operands: they are implicitly converted to numbers. + operator with Object operand (concatenation).