Node.js 节点js服务器在PUT请求后崩溃

发出put请求后，应用程序因错误而崩溃

[nodemon] restarting due to changes...
[nodemon] starting `node index.js`
(node:21666) DeprecationWarning: current URL string parser is deprecated, and will be removed in a future version. To use the new parser, pass option { useNewUrlParser: true } to MongoClient.connect.
(Use `node --trace-deprecation ...` to show where the warning was created)
Server up and running
(node:21666) DeprecationWarning: Mongoose: `findOneAndUpdate()` and `findOneAndDelete()` without the `useFindAndModify` option set to false are deprecated. See: https://mongoosejs.com/docs/deprecations.html#findandmodify
node:internal/process/promises:227
          triggerUncaughtException(err, true /* fromPromise */);
          ^

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at new NodeError (node:internal/errors:329:5)
    at ServerResponse.setHeader (node:_http_outgoing:572:11)
    at ServerResponse.header (/Users/kayode/Desktop/learn-mern/auth/node_modules/express/lib/response.js:771:10)
    at ServerResponse.json (/Users/kayode/Desktop/learn-mern/auth/node_modules/express/lib/response.js:264:10)
    at ServerResponse.send (/Users/kayode/Desktop/learn-mern/auth/node_modules/express/lib/response.js:158:21)
    at /Users/kayode/Desktop/learn-mern/auth/routes/users.js:36:24
    at processTicksAndRejections (node:internal/process/task_queues:94:5) {
  code: 'ERR_HTTP_HEADERS_SENT'
}
[nodemon] app crashed - waiting for file changes before starting...

这是我的密码

const router = require('express').Router();
const User = require('../models/User')

router.put('/:email', async (req, res, next) => {
    res.send(req.params._id)
    let email = req.params.email;
    let user = {
        name: req.body.name,
        email: req.body.email,
        password: req.body.password
    }

    try {
        await User.findOneAndUpdate(email, user);
        res.status(200).send(JSON.stringify('200'));
        console.log('Here first')
    } catch (err) {
        res.status(400).send(err) //not commented
    }
})

module.exports = router;

但是，如果我尝试发出另一个请求（使用postman），而不刷新服务器，它会说发送错误无法发送请求

但是，在第36行，“at/Users/kayode/Desktop/learn mern/auth/routes/Users.js:36:24”，上面写着

res.status（400）.send（err）//未评论

如果我将行注释掉（即不返回错误），PUT请求将成功，之后的另一个请求也将在不刷新或重新启动服务器的情况下工作

---

我知道我可以评论这句话，然后继续，但我需要知道发生了什么，谢谢

您在请求开始时发送响应，并在请求结束时再次尝试发送响应（第5行）

---

删除此行

res.send（请求参数_id）

。仅当返回对数据库的请求时才调用res.send（）。你也能分享一下你当时为什么这么做（res.send（req.params._id））吗？@joyce obi，谢谢！那是我的一个愚蠢的打字错误。我用这个id找到了一个用户，又改回使用电子邮件，但忘了编辑它。哦，好吧，很好，它已经被修复了。

const router = require('express').Router();
const User = require('../models/User')

router.put('/:email', async (req, res, next) => {
    let email = req.params.email;
    let user = {
        name: req.body.name,
        email: req.body.email,
        password: req.body.password
    }

    try {
        await User.findOneAndUpdate(email, user);
        res.status(200).send(JSON.stringify('200'));
        console.log('Here first')
    } catch (err) {
        res.status(400).send(err) //not commented
    }
})

module.exports = router;