开关盒未显示正确结果

问题描述

我是JavaScript的新手.这是我的剧本

i am a a newbie in javascript.here is my script

        var marks=11;
    switch(marks){
        case (marks<20):
        console.log('Yes Freaking Failed');
        break;
        case (marks>20):
        console.log('Ahh Its Ok');
        break;
        case (marks>80):
        console.log('Whooping');
        break;
        default:
        console.log('Cant say u maybe Flunked');
        break;
    }

现在我认为它应该显示Yes Freaking Failed，因为标记少于20.但是它显示了can't say..为什么?请告诉我我在哪里做错了.谢谢.

Now i think it should display Yes Freaking Failed because the marks are less than 20. But it shows can't say.. why is that?Please tell me where i am doing it wrong.thanks.

推荐答案

撰写时

switch (x) {
case(y):
    ...
}

相当于测试

if (x == y) {
    ...
}

所以

case (marks < 20):

表示:

if (marks == (marks < 20)) {

您不能将case用于此类范围测试，需要使用一系列if/else if:

You can't use case for range tests like this, you need to use a series of if/else if:

if (marks < 20) {
    console.log('Yes Freaking Failed');
} else if (marks < 80) {
    console.log('Ahh Its OK');
} else {
    console.log('Whooping');
}

还要注意，如果它按照您的想法工作，它将永远不会执行marks > 80，因为它也将匹配marks > 20，并且始终执行第一个匹配的大小写.

Also notice that if it worked the way you thought, it could never execute marks > 80, because that would also match marks > 20, and the first matching case is always executed.

不需要Cant say u maybe flunked情况，因为没有其他可能性.

There's no need for the Cant say u maybe flunked case, because there are no other possibilities.

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