是否可以在switch语句中使用.contains()? [英] Is it possible to use .contains() in a switch statement?

问题描述

这只是我要执行的操作的一个简单示例:

This is just a simple example of what I'm trying to do:

switch (window.location.href.contains('')) {
    case "google":
        searchWithGoogle();
        break;
    case "yahoo":
        searchWithYahoo();
        break;
    default:
        console.log("no search engine found");
}

如果不可能/不可行，有什么更好的选择?

If it's not possible/feasible what would be a better alternative?

解决方案:

在阅读了一些答复之后，我发现以下是一个简单的解决方案.

After reading some of the responses I found the following to be a simple solution.

function winLocation(term) {
    return window.location.href.contains(term);
}
switch (true) {
    case winLocation("google"):
        searchWithGoogle();
        break;
    case winLocation("yahoo"):
        searchWithYahoo();
        break;
    default:
        console.log("no search engine found");
}

推荐答案

是"，但不会满足您的期望.

"Yes", but it won't do what you expect.

用于开关的表达式一次被评估 -在这种情况下，包含的结果将被评估为true/false(例如， switch(true)或 switch(false))，而不是可以匹配的字符串.

The expression used for the switch is evaluated once - in this case contains evaluates to true/false as the result (e.g. switch(true) or switch(false)) , not a string that can be matched in a case.

因此，以上方法无效.除非此模式更大/可扩展，否则请使用简单的if/else-if语句.

As such, the above approach won't work. Unless this pattern is much larger/extensible, just use simple if/else-if statements.

var loc = ..
if (loc.contains("google")) {
  ..
} else if (loc.contains("yahoo")) {
  ..
} else {
  ..
}

但是，请考虑是否有一个 classify 函数返回了"google"或"yahoo"等信息，也许使用了上述条件.然后可以原样使用它，但在这种情况下可能会造成过大杀伤力.

However, consider if there was a classify function that returned "google" or "yahoo", etc, perhaps using conditionals as above. Then it could be used as so, but is likely overkill in this case.

switch (classify(loc)) {
   case "google": ..
   case "yahoo": ..
   ..
}

---

尽管以上在JavaScript中进行了讨论，但Ruby和Scala(以及可能的其他工具)提供了处理更多高级开关"用法的机制.

---

While the above discusses such in JavaScript, Ruby and Scala (and likely others) provide mechanisms to handle some more "advanced switch" usage.

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