Javascript 和编程新手。我的代码错误？

Question

您好，我是 JavaScript 和一般编程的新手。我一直在使用 Codecademy 来帮助我学习。但是，我最近在 Codecademy 中创建的一组代码遇到了问题，我似乎找不到问题所在。代码如下：

var mInQuestion = prompt('Do you play a musical instrument?').toLowerCase;
if (mInQuestion == yes) {
var musInstrument = prompt('Which instrument do you play?').toLowerCase;
switch (musInstrument) {
    case 'piano':
        console.log('Oh great! Piano is wonderful!');
        break;
    case 'guitar':
        console.log('Wow I love guitar as well!');
        experience = prompt('Did you play when you were little?').toLowerCase;
        interest = prompt('And do you like playing it?')toLowerCase;
        if (experience && interest == yes||y) {
            console.log("That's great! You must be a guitar master!");
        }
        else {
            console.log("Keep learning! It will be great. Or you could do piano?");
        }
        break;
    case 'flute':
        console.log('Oh that\'s cool! You know I used to play flute as well!');
        break;
    default:
        console.log('Oh I\'m not sure I\'ve heard of that instrument...sorry');
        break;
}
else if (mInQuestion == no) {
console.log('Oh you don\'t? You should pick one like the piano or the guitar!');
}
else {
console.log('Your answer doesn\'t make sense...');
}

Answer 1

看这里的这一行：

if (mInQuestion == yes) {

您正在尝试检查mInQuestion 是否是字符串"yes"，但实际上您是在检查它是否等于不存在的变量yes。在yes 和no 周围加上引号。

还要注意这一行：

if (experience && interest == yes||y) {

您不能像这样检查多个条件，每次检查都必须明确：

if ((experience == 'yes' || experience == 'y') && (interest == 'yes' || interest == 'y'))

此外，您尝试拨打toLowerCase 的任何地方都是不正确的。您正在尝试调用一个函数，但忽略了括号。这意味着您的变量实际上是函数，而不是您想要的字符串。在每次调用toLowerCase后加括号

Answer 2

您的吉他有一些问题。您需要声明经验和兴趣这两个变量，另外还缺少一个 .在小写之前。您的 if 语句末尾还缺少一个右括号 }。如果您正在测试字符串，您的 if 语句也需要使用引号进行格式化，并且每个条件都需要完整地写出。

 var mInQuestion = prompt('Do you play a musical instrument?').toLowerCase;
if (mInQuestion == yes) {
    var musInstrument = prompt('Which instrument do you play?').toLowerCase;
    switch (musInstrument) {
        case 'piano':
            console.log('Oh great! Piano is wonderful!');
            break;
        case 'guitar':
            console.log('Wow I love guitar as well!');
            var experience = prompt('Did you play when you were little?').toLowerCase; //need to declare these
            var interest = prompt('And do you like playing it?').toLowerCase;
            if ((experience ==='yes' ||experience==='y') && (interest === 'yes'|| interest ==='y')) {
                console.log("That's great! You must be a guitar master!");
            }
            else {
                console.log("Keep learning! It will be great. Or you could do piano?");
            }
            break;
        case 'flute':
            console.log('Oh that\'s cool! You know I used to play flute as well!');
            break;
        default:
            console.log('Oh I\'m not sure I\'ve heard of that instrument...sorry');
            break;
    }} //need bracket here
else if (mInQuestion == no) {
    console.log('Oh you don\'t? You should pick one like the piano or the guitar!');
}
else {
    console.log('Your answer doesn\'t make sense...');
}

Answer 3

语法错误遗漏。这里 interest = prompt('你喜欢玩吗？')toLowerCase;

 break;
case 'guitar':
    console.log('Wow I love guitar as well!');
    experience = prompt('Did you play when you were little?').toLowerCase;
    interest = prompt('And do you like playing it?').toLowerCase;
    if (experience && interest == yes||y) {
        console.log("That's great! You must be a guitar master!");
    }

Answer 4

三个问题：

1. 上面的toLowerCase 应该是toLowerCase()（无处不在）。前者是对函数的引用。后者调用函数并返回等效的小写字符串。

2. 除非您在某处声明了变量 yes，否则您可能希望将该字符串放在引号中，例如"yes"。对于no 和y（可能还有n，某处）也是如此。

3. 导致Unexpected identifier 错误的原因在这里：

   if (experience && interest == yes||y) {
   

   要将变量与两个值进行比较，请分别进行：

   if (experience && (interest == yes || interest == y)) {
   

Answer 5

很多语法错误。您有变量正在比较提示中的输入，例如 mInQuestion == yes，这是不正确的（除非您有一个名为 yes 的变量。这需要更改为 mInQuestion == 'yes'。在整个代码中还有许多其他类似的问题. 此外，您的第一个 if 语句中还缺少右大括号 }。您还忘记调用一些函数，例如 toLowerCase()。

var mInQuestion = prompt('Do you play a musical instrument?').toLowerCase(); // <--forgot to invoke
if (mInQuestion == 'yes') { // <-- changed to 'yes'
    var musInstrument = prompt('Which instrument do you play?').toLowerCase(); // <--forgot to invoke
    switch (musInstrument) {
        case 'piano':
            console.log('Oh great! Piano is wonderful!');
            break;
        case 'guitar':
            console.log('Wow I love guitar as well!');
            experience = prompt('Did you play when you were little?').toLowerCase(); // <--forgot to invoke
            interest = prompt('And do you like playing it?').toLowerCase(); // <--forgot to invoke and forgot period
            if (experience && interest == 'yes' || 'y') { // <-- changed to 'yes' and 'y'
                console.log("That's great! You must be a guitar master!");
            }
            else {
                console.log("Keep learning! It will be great. Or you could do piano?");
            }
            break;
        case 'flute':
            console.log('Oh that\'s cool! You know I used to play flute as well!');
            break;
        default:
            console.log('Oh I\'m not sure I\'ve heard of that instrument...sorry');
            break;
    }
} // <--Added closing curly brace
else if (mInQuestion == 'no') { // <-- changed to 'no'
    console.log('Oh you don\'t? You should pick one like the piano or the guitar!');
}
else {
    console.log('Your answer doesn\'t make sense...');
}

Answer 6

您的 js 中有几个错误/错误。

这是其中之一：

    if (experience && interest == yes||y) {
        console.log("That's great! You must be a guitar master!");
    }

应该是

    if ( (experience == yes|| y ) && ( interest == yes||y) ) {
        console.log("That's great! You must be a guitar master!");
    }

因为它之前的编写方式，（经验 && 兴趣 == 是||y），经验只需要有一个值（它可以是除 0 或 null 之外的任何值）并且它将作为 True 传递。