Question

我正在尝试创建一个涉及switch（）的函数，并根据特定的随机生成的数字给出答案。不知怎的，我的函数没有运行它应该运行的情况。它只给出了默认情况，无论数字是多少。

这是我的代码：

var i;
var girl;

function response() {
    var girl = prompt("What girl do you like?");
    var r = (Math.random() * (3 - 1 + 1) + 1).toFixed(0);
    var i = r;

    switch(i) {
        case (i == 1):
            alert(girl + " likes you as a friend.");
            break;

        case (i == 2):
            alert(girl + " does not really like you.");
            break;

        case (i == 3):
            alert(girl + " has a crush on you.");
            break;

        case (i == 4):
            alert(girl + " wants you to ask her out.");
            break;

        default:
            console.log(i);
    }
}

Answer 1

这不是开关的工作原理。它会将每个case的值与switch进行比较。

现在基本上，它将i的值多次与布尔值（例如i == 1的结果）进行比较。

此外，通过将静态值的算术添加到值中，您的随机性不会变得更随机。您应该将其替换为4。你也应该使用像Math.ceil()这样的东西（因为你忽略了0值，这也许不是一个好主意），而不是toFixed()返回一个字符串。

您也不需要围绕值进行比较的括号。如果您知道随机数的范围，您可能也不需要默认情况（因为您已经涵盖了所有可能性）。

您也可以直接使用r，无需重新分配。

您的变量也是您的函数的本地变量，因此可能不需要它们在顶部。

以下是我将如何重写：

function response() {
    var girl = prompt("What girl do you like?");
    var r = Math.floor(Math.random() * 4);

    switch(r) {
        case 0:
            alert(girl + " likes you as a friend.");
            break;

        case 1:
            alert(girl + " does not really like you.");
            break;

        case 2:
            alert(girl + " has a crush on you.");
            break;

        case 3:
            alert(girl + " wants you to ask her out.");
            break;

    }
}

......甚至......

function response() {
    var answerSuffixes = [
        " likes you as a friend.",
        " does not really like you.",
        " has a crush on you.",
        " wants you to ask her out."
    ];
    var girl = prompt("What girl do you like?");
    var r = Math.floor(Math.random() * answerSuffixes.length);

    alert(girl + answerSuffixes[r]);
}

Answer 2

Javascript中的case语句已经在目标i上匹配：

switch(i) {
        case 1:
            alert(girl + " likes you as a friend.");
            break;

        case 2:
            alert(girl + " does not really like you.");
            break;

        case 3:
            alert(girl + " has a crush on you.");
            break;

        case 4:
            alert(girl + " wants you to ask her out.");
            break;

        default:
            console.log(i);
    }

因此，不需要在每个case中使用比较表达式。

Answer 3

switch正在比较严格。

你需要

switch (i) {
    case 1:
        alert(girl + " likes you as a friend.");
        break;

或者

switch (true) {
    case i === 1:
        alert(girl + " likes you as a friend.");
        break;

Answer 4

当您声明一个开关时，将使用的变量与每种情况进行比较，因此不需要进行评估。

为了保持变量类型的检查，将'r'的答案解析为整数也可能有帮助。

function response() {
    var girl = prompt("What girl do you like?");
    var r = parseInt((Math.random() * (3 - 1 + 1) + 1).toFixed(0));
    var i = r;

    switch(i) {
        case 1:
            alert(girl + " likes you as a friend.");
            break;

        case 2:
            alert(girl + " does not really like you.");
            break;

        case 3:
            alert(girl + " has a crush on you.");
            break;

        case 4:
            alert(girl + " wants you to ask her out.");
            break;

        default:
            console.log(i);
   }
}

Switch（）不适用于Math.random（）数字

4 个答案: