如何将存储在 switch 语句内的变量中的大写转换为小写

Question

这是我的javascript代码，它应该显示：Okay! Great choice We are working hard for your cake如果我输入cake 或Cake(注意 c 与大写字母(，但与cake一起工作得很好，但不能与Cake一起使用，pancake和大写 pPancake也是如此：

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

"cake" || "Cake"表达式的计算结果为 true，因为这两个字符串都是真实的。因此，当用户的输入与该值进行比较时，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，您可以在比较之前将其转换为小写(通过make.toLowerCase()(：

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.");
}

如果你不熟悉真值或假值的概念，你可以在这里阅读MDN的文档：https://developer.mozilla.org/en-US/docs/Glossary/Truthy https://developer.mozilla.org/en-US/docs/Glossary/falsy

Answer 2

如果左侧为 true 值，则||运算符的计算结果为左侧，否则计算为右侧。

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

因此case ("cake" || "Cake"):意味着case ("cake"):。

---

如果要在交换机中有多个匹配项，请具有多个案例。

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

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.");
}