Expess 中的 UnhandledPromiseRejectionWarning 错误

Question

const Car = mongoose.model('Car', new mongoose.Schema({
  name: {
    type: String,
    required: true,
  }
}));


router.put('/:id', async (req, res) => {
  const { error } = joiValidator(req.body); 
  if (error) return res.status(400).send(error.details[0].message)

  try {
    const car= await Car.findByIdAndUpdate(req.params.id, { name: req.body.name }, {new: true })
  } catch (error) {
    return res.status(404).send('not found.');
  }  
  
  res.send(car);
})

i am successfully connected to mongoDB using mongoose, its only when i try to mock an error by giving a wrong id as an input i get the following error, even though i handled async and await with the trycatch block

(node:19392) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:19392) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

Answer 1

This is mainly because you are using try an catch after an if. In javascript the way of reading code is asynchronous so, if and try are executed at the same time. Also, you don´t need to use an async function here, as you are only calling one promise.

Here I let you a simpler code without async.

router.put("/:id", (req, res) => {
  const { error } = joiValidator(req.body);
  if (error) {
    return res.status(400).send(error.details[0].message);
  } else {
    Car.findByIdAndUpdate(req.params.id,{ name: req.body.name },{ new: true },(err, car) => {
        if (err) return res.status(404).send({ message: 'Not found', err });
        return res.status(200).send(car);
      }
    );
  }
});