Question

这是我的JavaScript代码，应该显示：Okay! Great choice We are working hard for your cake，如果我输入cak e或Cake（注意c用大写字母表示），但可以与cake一起使用，但是Cake不适用，pancake和大写字母p Pancake也一样：

var make=prompt("Hey! What you are up to cake or pancake?");
switch(make){
    case ("cake" || "Cake"):
    console.log("Okay! Great choice  We are working hard for your cake");
    break;
    case ("pancake" || "Pancake"):
        console.log("Okay! Great choice   We are working hard for your pancake");
    break;
    default:
    console.log("Sorry we Only have cake or pancake to choose from.");
}

Answer 1

如果||运算符的左侧为真值，则将其评估为左侧，否则，其评估将为右侧。

所以"cake" || "Cake"因为"cake"是一个真值，所以意味着"cake"。

因此case ("cake" || "Cake"):的意思是case ("cake"):。

如果您想在一个开关中有多个匹配项，请有多种情况。

case ("cake"):
case ("Cake"):
    // etc
    break;

Answer 2

表达式"cake" || "Cake"的计算结果为true，因为这两个字符串都是 truthy 。因此，当将用户输入的值与该值进行比较时，例如"cake" == true，它的计算结果为true，因为用户的输入（"cake"）也是真实的。

要忽略用户输入的大小写，只需在比较之前将其转换为小写（通过make.toLowerCase()）即可。

var make = prompt("Hey! What you are up to cake or pancake?");
switch (make.toLowerCase()) {
  case "cake":
    console.log("Okay! Great choice  We are working hard for your cake");
    break;
  case "pancake":
    console.log("Okay! Great choice   We are working hard for your pancake");
    break;
  default:
    console.log("Sorry we Only have cake or pancake to choose from.");
}

如果您不熟悉 truthy 或 falsy 值的概念，则可以在此处阅读MDN的文档：https://developer.mozilla.org/en-US/docs/Glossary/Truthy和https://developer.mozilla.org/en-US/docs/Glossary/falsy < / p>

Answer 3

不变比较：

var make = prompt("Hey! What you are up to cake or pancake?");

if (make.localeCompare("cake".toUpperCase()) == -1) {
  console.log("Okay! Great choice  We are working hard for your cake");
} else if (make.localeCompare("pancake".toUpperCase()) == -1) {
  console.log("Okay! Great choice   We are working hard for your pancake");
} else {
  console.log("Sorry we Only have cake or pancake to choose from.");
}

如何将大写字母转换为小写字母并存储在开关语句中的变量中

3 个答案: