jquery 在切换案例中使用范围?

jquery Using ranges in switch cases?(jquery 在切换案例中使用范围?)

问题描述

开关盒通常是这样的

Monday: 
Tuesday: 
Wednesday: 
etc. 

我想使用范围.

from 1-12: 
from 13-19:
from 20-21:
from 22-30:

有可能吗?顺便说一句，我正在使用 javascript/jquery.

Is it possible? I'm using javascript/jquery by the way.

推荐答案

你可以尝试滥用开关跌倒行为

you could try abusing the switch fall through behaviour

var x = 5;
switch (x) {
    case  1: case 2: case 3: case 4: ...
        break;
    case 13: case 14: case 15: ...
        break;
    ...
}

非常冗长

或者你可以试试这个

function checkRange(x, n, m) {
    if (x >= n && x <= m) { return x; }
    else { return !x; }
}

var x = 5;
switch (x) {
    case checkRange(x, 1, 12):
        //do something
        break;
    case checkRange(x, 13, 19):
    ...
}

这会让你得到你想要的行为.我在 checkRange 的 else 中返回 !x 的原因是为了防止将 undefined 传递到 switch 语句时出现问题.如果您的函数返回 undefined (就像 jdk 的示例一样)并且您将 undefined 传递给开关，那么第一个案例将被执行.!x 保证在任何相等性测试下都不等于 x，这是 switch 语句选择执行哪种情况的方式.

this gets you the behaviour you would like. The reason i return !x in the else of checkRange is to prevent the problem of when you pass undefined into the switch statement. if your function returns undefined (as jdk's example does) and you pass undefined into the switch, then the first case will be executed. !x is guaranteed to not equal x under any test of equality, which is how the switch statement chooses which case to execute.

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