问题

I understand your request. Here's the translated code portion without the parts you mentioned not to translate:

我正在处理一个具有以下路由的 API（全部都是 POST 请求）

`/friends?d=onlineFriends`
`/friends?d=offlineFriends`
等等…

以及它是如何处理的：

`server.js`
```js
app.post("/friends", (req, res, next) => {
  let d = req.query.d;
  let path = "./funcs/" + d + ".js";
  return require(path)(req, res, next);
})

./funcs/onlineFriends.js

module.exports = (req, res, next) => {
  return res.sendStatus(200);
}

但问题是，我想为每个函数使用不同的中间件。使用上面的代码，如果我想使用中间件，它将应用于所有函数，因为你必须将它放在 app.post 部分。

我尝试过以下方法：

module.exports = (req, res, next) => {
  middleware(req, res, next);
  return res.sendStatus(200);
}

但当然会导致 Cannot set headers after they are sent to the client 错误。

我知道你可能会问：“为什么不使用像 /friends/online 这样的路由？”但我真的无法更改客户端，我必须这样做。

Please note that I've translated the code portion while excluding the parts you specified not to translate.

<details>
<summary>英文:</summary>

I&#39;m working on an API that has routes like this (all POST requests)

`/friends?d=onlineFriends`
`/friends?d=offlineFriends`
and on...

and this is how it&#39;s handled:

`server.js`
```js
app.post(&quot;/friends&quot;, (req, res, next) =&gt; {
  let d = req.query.d
  let path &quot;./funcs/&quot; + d + &quot;.js&quot;
  return require(path)(req, res, next)
})

./funcs/onlineFriends.js

module.exports = (req, res, next) => {
  return res.sendStatus(200)
}

But the thing is, I want to use different middlewares per func, with the code above if I wanted to use a middleware it would apply to all funcs because you'd have to put it in app.post part.

I've tried following:

module.exports = (req, res, next) => {
  middleware(req, res, next)
  return res.sendStatus(200)
}

but of course it results in Cannot set headers after they are sent to the client.

I know you might ask "Why not use a router like /friends/online", I really can't change the client and this is how I must do it.

答案1

得分: 1

如果您有中间件 a、b 和 c，您可以动态选择它们的组合并使用它们来处理请求：

app.post("/friends", function(req, res, next) {
  var middleware;
  switch (req.query.d) {
    case "a": middleware = [a, c]; break;
    case "b": middleware = [b]; break;
    default: return next();
  }
  express.Router().use(middleware)(req, res, next);
});

app.post("/friends", function(req, res, next) {
  var middleware;
  switch (req.query.d) {
    case "a": middleware = [a, c]; break;
    case "b": middleware = [b]; break;
    default: return next();
  }
  express.Router().use(middleware)(req, res, next);
});