JavaScript的菜鳥級語法錯誤

-1

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 :("); 
}

我越來越：JavaScript的菜鳥級語法錯誤

SyntaxError: Unexpected token 'else'

如果有人可以幫助我，將是巨大的:)

來源

2014-02-20 user3290967

變化'如果（userAnswer）「是」;''來，如果（userAnswer == 「是」）{' – Bart

@SamuelLiew您剛纔編輯自己的錯誤離開這個問題？沒有人知道上下文了。 – A1rPun

這是系統的提示，需要比較userAnswer您的價值：

if (userAnswer) "yes";

無效。改變

if (userAnswer == "yes")

然而，這隻會工作，如果用戶鍵入「是」準確，而不是「OK」，「是啊！」或類似的。

爲了避免這種情況，您可以使用確認對話框，它將提供兩個選項「確定」或「取消」。

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

來源

2014-02-20 12:54:44

其實你呢。提示需要用戶輸入字符串，因此如果用戶輸入「否」，提示將返回「否」，其結果爲「真」。 – Bart

中，如果循環

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 :("); 
}

來源

2014-02-20 12:56:05

如果不是循環而是控制（條件）結構;） – Christoph

你在你的第二個if語句有錯誤刪除;。

if (userAnswer == "yes");

來源

2014-02-20 12:56:06 kale909

-1

因爲顯然沒有人知道，及時返回一個字符串，在這裏我們去：

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 :("); 
}

來源

2014-02-20 12:59:32 Bart

您需要更改

if (userAnswer) "yes"; 
{ 
}

要

if (userAnswer == "yes") 
{ 
}

爲什麼？

聲明if (userAnswer) "yes";表示檢查userAnswer是否有一個值（if(userAnswer)），然後是一個意外的令牌"yes";。

正確的答案是如何工作的？

if (userAnswer == "yes")表示通過使用==運算符來檢查userAnswer是否等於「yes」，該運算符是許多編程語言中的常見比較運算符。

提示：您可能希望使用if (userAnswer.toUpperCase() == "YES")，因爲它意味着yes可以在任何情況下進入，例如yEs和YEs ...

來源

2014-02-20 13:00:11 Joseph

將prompt更改爲confirm並檢查返回的布爾值會更穩健。

使用prompt將返回一個字符串，您明確必須檢查某個值（例如，通過正則表達式或一組可能的有效答案）。如果用戶鍵入For sure或Hell, yeah!或甚至簡單YES您的支票userAnswer == "yes"將失敗。

所以最好使用這個：

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

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

來源

2014-02-20 13:00:19 Christoph

JavaScript的菜鳥級語法錯誤

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