如果do/while语句无限循环javascript中的其他语句

Question

我正试图使js中的do/while循环和逻辑运算符保持清醒。我的问题是在do部分中嵌入if/ else if/ else语句时，它一直在循环警报。另外，如果我键入的不是罕见的、中等的或做得好的，那么它会进入else if语句，而不是else语句，即使我已经为else if语句指定了中介语句或做得好的语句。我哪里出问题了？任何帮助都将不胜感激。

谢谢。

var food;
var steak;

food = prompt("Hey what type of food do you want to eat? We have steak,                  chicken, legumes, kangaroo or pufferfish?","Select your choice   here.").toUpperCase();

switch (food) {
    case 'STEAK':
        alert ("Sure no problem, how would you like your steak done?");
        steak = prompt("Would you like your steak done rare, medium or well-done?").toUpperCase();
            do {
                if (steak === "RARE") {
                    alert ("You eat the rare steak");
                }
                else if (steak === "MEDIUM"||"WELL-DONE") {
                    alert("You eat your steak and it's good.");
                }
                else {
                    alert("Sorry didn't catch that.");
                    steak = prompt("Choose rare, medium or well-done.");
                }
            } while (steak !== "RARE" || "MEDIUM" || "WELL-DONE");
        break;
}

Answer 1

它是无限循环的，因为'while‘结构中的条件总是等同于"true“。

你所拥有的如下：

while (steak !== "RARE" || "MEDIUM" || "WELL-DONE")

把它改成

while (steak !== "RARE" && steak !== "MEDIUM" && steak !== "WELL-DONE")

另外，在其中一个“else if”语句中也有类似的问题。

else if (steak === "MEDIUM"||"WELL-DONE") {

把它改成

else if (steak === "MEDIUM"|| steak === "WELL-DONE") {

在您的脚本中仍然存在一些逻辑问题。试一试以下几种方法：

var food;
var steak;

food = prompt("Hey what type of food do you want to eat? We have steak,                  chicken, legumes, kangaroo or pufferfish?","Select your choice   here.").toUpperCase();

switch (food) {
case 'STEAK':
    alert ("Sure no problem, how would you like your steak done?");

    steak = prompt("Would you like your steak done rare, medium or well-done?").toUpperCase();
    while (steak !== "RARE" && steak !== "MEDIUM" && steak !== "WELL-DONE") {
        alert("Sorry didn't catch that.");
        steak = prompt("Choose rare, medium or well-done.").toUpperCase();
    }

    if (steak === "RARE") {
        alert ("You eat the rare steak");
    }
    else if (steak === "MEDIUM"|| steak === "WELL-DONE") {
        alert("You eat your steak and it's good.");
    }            
    break;
}

如果还不起作用的话请告诉我。

Answer 2

你必须逐个做比较，所以

else if (steak === "MEDIUM"||"WELL-DONE") {
    alert("You eat your steak and it's good.");
}

应该是

else if (steak === "MEDIUM"|| steak === "WELL-DONE") {
    alert("You eat your steak and it's good.");
}

诸若此类。这也是无限do/while循环的原因。

Answer 3

如前所述，这些条件必须单独进行测试，即

 if (a == n || a == m)

还有你最后的说法不对。你可能会想做这样的事

​

var food;
var steak;

food = prompt("Hey what type of food do you want to eat? We have steak,                  chicken, legumes, kangaroo or pufferfish?","Select your choice   here.").toUpperCase();

switch (food) {
    case 'STEAK':
        alert ("Sure no problem, how would you like your steak done?");
        steak = prompt("Would you like your steak done rare, medium or well-done?").toUpperCase();
        console.log('steak', steak);
            do {
                console.log('steak inside do', steak);
                if (steak === "RARE") {
                    alert ("You eat the rare steak");
                }
                else if (steak === "MEDIUM"|| steak ==="WELL-DONE") {
                    alert("You eat your steak and it's good.");
                }
                else {
                    alert("Sorry didn't catch that.");
                    steak = prompt("Choose rare, medium or well-done.").toUpperCase();
                }
            } while (steak !== "RARE" && steak !== "MEDIUM" && steak !== "WELL-DONE");
        break;
}

​

为我工作过。