javascript - 为什么输出应该去到 "undefined"项？

Question

输出应该看起来像“Tuesday, July 26, 2016”，然后是“enjoy”，但是，它看起来像 “周二 七月 未定义,未定义 26 , 2016 星期二”

这是我的代码: var 今天 = new Date();

function getMonth1(today) {
    if(today.getMonth() == 0) {
        console.log("January");
    }
    else if(today.getMonth() == 1) {
        console.log("February");
    }
    else if(today.getMonth() == 2) {
        console.log("March");
    }
    else if(today.getMonth() == 3) {
        console.log("April");
    }
    else if(today.getMonth() == 4) {
        console.log("May");
    }
    else if(today.getMonth() == 5) {
        console.log("June");
    }
    else if(today.getMonth() == 6) {
        console.log("July");
    }
    else if(today.getMonth() == 7) {
        console.log("August");
    }
    else if(today.getMonth() == 8) {
        console.log("September");
    }
    else if(today.getMonth() == 9) {
        console.log("October");
    }
    else if(today.getMonth() == 10) {
        console.log("November");
    }
    else if(today.getMonth() == 11) {
        console.log("December");
    }
}

function getWeekday(today) {
    if(today.getDay() == 0) {
        console.log("Sunday");
    }
    else if(today.getDay() == 1)    {
        console.log("Monday");
    }
    else if(today.getDay() == 2)    {
        console.log("Tuesday");
    }
    else if(today.getDay() == 3)    {
        console.log("Wednesday");
    }
    else if(today.getDay() == 4)    {
        console.log("Thursday");
    }
    else if(today.getDay() == 5)    {
        console.log("Friday");
    }
    else if(today.getDay() == 6)    {
        console.log("Saturday");
    }
}


function getDate1(today) {
    console.log(getWeekday(today) + "," + getMonth1(today), today.getDate(), ",", today.getFullYear());
    if(getWeekday(today) == "Tuesday") { 
        console.log("enjoy");
     }
    }

getDate1(今天);

Answer 1

除了必须像 Jaromanda X 提到的那样返回一个值之外，您还可以像这样简化代码(如 Touffy 提到的数组查找):

function getWeekDay(index) {
    return 
    ["Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"][index];
}

然后使用getDay()调用它:

alert(getWeekDay(new Date().getDay()));

然后使用 getMonth() 调用它，对月份进行类似的设置。