Question

var age = Number(prompt("How old are you?"));

if(age >= 13) {
    console.log("You are old enough!");
    alert("You Are old enough!");
    console.log("You are at a Justin Bieber concert, and you hear this lyric 'Lace my shoes off, start racing.'");
    console.log("Suddenly, Bieber stops and says, 'Who wants to race me?'");

    var userAnswer = prompt("Do you want to race Bieber on stage?");
    if(userAnswer) "yes";
    {
        console.log("You and Bieber start racing. It's neck and neck! You win by a shoelace!");
    } else {
        console.log("Oh no! Bieber shakes his head and sings 'I set a pace, so I can race without pacing.'");
    }
} else {
    console.log("Sorry, You Are Not old Enough :( ");
    alert("Sorry, You Are Not old Enough :( ");
}

我得到了：

SyntaxError：意外的标记'else'

如果有人能帮助我，那就太棒了:)

Answer 1

您需要更改

if (userAnswer) "yes";
{
}

要

if (userAnswer == "yes")
{
}

为什么？

声明if (userAnswer) "yes";表示检查userAnswer是否有值（if(userAnswer)），然后是"yes";的意外标记。

正确的答案如何运作？

if (userAnswer == "yes")表示使用==运算符检查userAnswer是否等于“是”，这是许多编程语言中常见的比较运算符。

提示：您可能希望使用if (userAnswer.toUpperCase() == "YES")，因为这意味着可以在任何情况下输入yes，例如yEs和YEs ...

Answer 2

这是针对提示，您需要将userAnswer与您的值进行比较：

if (userAnswer) "yes";

无效。改为

if (userAnswer == "yes")

但是，这只有在用户输入“是”时才有效，而不是“确定”，“是的！”或类似的。

为避免这种情况，您可以使用确认对话框，它将提供两个选项“确定”或“取消”。

if(confirm("Do you want to race Bieber on stage?")) {

Answer 3

你的第二个if语句中有错误。

if (userAnswer == "yes");

Answer 4

删除if循环中的;

age = prompt(" How old Are You ? ");
if( age >= 13) {
    console.log("You Are old Enough ! ");
    alert("You Are old Enough ! ");
    console.log("You are at a Justin Bieber concert, and you hear this lyric 'Lace my shoes off, start racing.'");
    console.log("Suddenly, Bieber stops and says, 'Who wants to race me?'");
    var userAnswer = prompt("Do you want to race Bieber on stage? ");
    if (userAnswer=="yes"){
        console.log("You and Bieber start racing. It's neck and neck! You win by a shoelace!");
   } else {
        console.log("Oh no! Bieber shakes his head and sings 'I set a pace, so I can race without pacing.'");
    }
} else {
    console.log("Sorry, You Are Not old Enough :( ");
    alert("Sorry, You Are Not old Enough :( ");
}

Answer 5

将prompt更改为confirm并检查随后返回的布尔值会更加健壮。

使用prompt将返回一个字符串，您明确必须检查某个值（例如，通过正则表达式或一组可能的有效答案）。如果用户输入For sure或Hell, yeah!或甚至简单YES，则您的支票userAnswer == "yes"将失败。

这样可以更好地使用它：

var userAnswer = confirm("Do you want to race Bieber on stage? ");

if (userAnswer){
   /*...*/

Answer 6

由于显然没有人知道提示返回字符串，所以我们转到：

age = prompt(" How old Are You ? ");
if( age >= 13) {
    console.log("You Are old Enough ! ");
    alert("You Are old Enough ! ");
    console.log("You are at a Justin Bieber concert, and you hear this lyric 'Lace my shoes off, start racing.'");
    console.log("Suddenly, Bieber stops and says, 'Who wants to race me?'");
    var userAnswer = prompt("Do you want to race Bieber on stage? ");
    if (userAnswer == "yes") {
        console.log("You and Bieber start racing. It's neck and neck! You win by a shoelace!");
   } else {
        console.log("Oh no! Bieber shakes his head and sings 'I set a pace, so I can race without pacing.'");
    }
} else {
    console.log("Sorry, You Are Not old Enough :( ");
    alert("Sorry, You Are Not old Enough :( ");
}

javascript noob level语法错误

6 个答案: