以下节点模块返回“未定义”，但为什么呢？

Question

下面是一个模块，它接受一个参数，一个数字，然后根据该数字是偶数还是奇数，分别添加或减去一个常量 magicNumber。然而，当我运行这段代码时，我只是得到“未定义”。我究竟做错了什么？

module.exports = (number) => {

    let answer;  //Answer is declared in the global scope
    const magicNumber = 5;  //magicNumber is declared in the global scope

    if (number % 2) {  //If the number is even
        add(number);  //run the number through the add function
    } else {  //otherwise run the number through the subtract function
        subtract(number);
    }

    function add(number){  //Function takes the number as argument, does the math, and returns the value of answer.
        answer = number + magicNumber;
        return answer;
    }

    function subtract(number){  //Function takes the number as argument, does the math, and returns the value of answer.
        answer = number - magicNumber;
        return answer;
    }
};

Answer 1

您导出的块没有返回任何内容，因此默认情况下它是未定义的。

module.exports = (number) => {
let answer;  //Answer is declared in the global scope
const magicNumber = 5;  //magicNumber is declared in the global scope

if (number % 2) {  //If the number is even
    return add(number);  //you should return here as well
} else {  //otherwise run the number through the subtract function
    return subtract(number);//you should return here as well 
}

function add(number){  //Function takes the number as argument, does the math, and returns the value of answer.
    answer = number + magicNumber;
    return answer;
}

function subtract(number){  //Function takes the number as argument, does the math, and returns the value of answer.
    answer = number - magicNumber;
    return answer;
}
};