 <p>Your <code>alert</code> call is using the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#-_.28Unary_Plus.29" rel="nofollow">unary <code>+</code> arithmetic operator</a>, which attempts to convert its operand (in this case <code>cityname</code>) to a number. Since <code>cityname</code> is a string, the unary <code>+</code> cannot convert it and returns <code>NaN</code> instead.</p>