遍歷數組執行“ else”，即使“ if”語句為真（Javascript）

Question

一個簡單的問題..不確定為什么會這樣...

問題：即使if語句為true，“ else ”也會運行。

在這種情況下...

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輸入的城市為“ Los Angelos”，它是變量“ theAnswers”的數組元素，表示應運行警報，程序應完成...

會發生什么。

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程序顯示else警報。然后顯示正確的警報（if）。 你自己看...

var theAnswers = ["New York City", "Chicago", "Los Angelos", "Cleveland", "Ohio", "Seattle", "Boston", "Miami", "Philadelphia"];

var userAnswer = prompt("I am thinking of a Major City.. guess which one it is?", "Los Angelos");
userAnswer = userAnswer.toLowerCase();

for (var i = 0; i < theAnswers.length; i++) {
    if (userAnswer === theAnswers[i].toLowerCase()) {
        alert("Good, your guess is correct. You get one point!");
        break;
    }

    else{
        alert("Hmm... not quite the City I was looking for... Better luck next time!");

    }
}

Answer 1

這是因為您在進行else每項檢查時else在else中顯示該消息。 它將顯示每個不匹配的城市的消息。 首先瀏覽所有城市，然后一次顯示結果：

var found = false;
for (var i = 0; i < theAnswers.length; i++) {
    if (userAnswer === theAnswers[i].toLowerCase()) {
        found = true;
        break;
    }
}
if (found) {
    alert("Good, your guess is correct. You get one point!");
}else{
    alert("Hmm... not quite the City I was looking for... Better luck next time!");
}

Answer 2

刪除for循環。 您不必遍歷數組就可以知道答案是否存在，只要知道它的位置就足夠了。 嘗試這個：

var theAnswers = ["New York City", "Chicago", "Los Angelos", "Cleveland", "Ohio", "Seattle", "Boston", "Miami", "Philadelphia"];
var userAnswer = prompt("I am thinking of a Major City.. guess which one it is?", "Los Angelos");

if (theAnswers.indexOf(userAnswer)>=0) {
    alert("Good, your guess is correct. You get one point!");
}else{
    alert("Hmm... not quite the City I was looking for... Better luck next time!");
}

小提琴

Answer 3

條件為真時，它實際上不執行“其他”。

if (userAnswer === theAnswers[i].toLowerCase())

第一次評估此條件時，i為0，因此Answers [i]為“紐約市”。