JavaScript如果“ x =（a || b || c）”语句不起作用

Question

我正在用javascript开发一个简单的三角函数程序，并且if和while语句不能正常运行，因为它们仅在第一个条件为true时才通过，即如果您输入Sine，它将起作用，但如果您输入Cosine或Tangent，则不会。

<script language="JavaScript">
var opposite = 1
var adjacent = 1
var hypotenuse = 1
var sct = "SohCahToa"
while (!(sct == ("Sine" || "Cosine" || "Tangent"))) {
    sct = prompt("Sine (unknown adjacent) / Cosine (unkown opposite side) / Tangent (unknown hypotenuse)")
    if (!(sct == ("Sine" || "Cosine" || "Tangent"))) {
        alert("Spelling error, please try again")
    }
}
if (sct == ("Sine" || "Cosine"))
    hypotenuse = prompt("What is the hypotenuse")
if (sct == ("Sine" || "Tangent"))
    opposite = prompt("What is the opposite side")
if (sct == ("Tangent" || "Cosine"))
    adjacent = prompt("What is the adjacent side")

谢谢（将代码另存为.html进行测试）

Answer 1

您的所有多个比较如下所示：

if (sct == ("Sine" || "Cosine" || "Tangent"))

需要更改为：

if (sct == "Sine" || sct == "Cosine" || sct == "Tangent")

为了解释，当你做到这一点("Sine" || "Cosine" || "Tangent")，计算结果只"Sine"所以if (sct == ("Sine" || "Cosine" || "Tangent"))是一样的if (sct == "Sine")，这显然不是你想要的。

这是应用了所有更正的代码：

var opposite = 1
var adjacent = 1
var hypotenuse = 1
var sct = "SohCahToa"
while (!(sct == "Sine" || sct == "Cosine" || sct == "Tangent")) {
    sct = prompt("Sine (unknown adjacent) / Cosine (unkown opposite side) / Tangent (unknown hypotenuse)")
    (!(sct == "Sine" || sct == "Cosine" || sct == "Tangent")) {
        alert("Spelling error, please try again")
    }
}
if (sct == "Sine" || sct == "Cosine")
    hypotenuse = prompt("What is the hypotenuse")
if (sct == "Sine" || sct == "Tangent")
    opposite = prompt("What is the opposite side")
if (sct == "Tangent" || sct == "Cosine")
    adjacent = prompt("What is the adjacent side")