是否可以在 switch 语句中使用 .contains() ?

问题描述

这只是我正在尝试做的一个简单示例:

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，那么更好的选择是什么?

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

解决方案:

在阅读了一些回复后，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

是的"，但它不会像你期望的那样.

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

用于切换的表达式被评估一次 - 在这种情况下，contains 评估结果为真/假(例如 switch(true) 或 switch(false)), 不是一个 case 中可以匹配的字符串.

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，上述方法行不通.除非此模式更大/可扩展，否则只需使用简单的 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，请考虑是否存在返回google"或yahoo"等的classify 函数，可能使用上述条件.然后它可以这样使用，但在这种情况下可能会过大.

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": ..
   ..
}

<小时>

虽然上面讨论了 JavaScript 中的此类问题，但 Ruby 和 Scala(可能还有其他)提供了处理一些更高级开关"使用的机制.

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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