node express try catch not working as expected

user_12902326 0
Viewed 1334

I'm a beginner in Node/Express.js and I'm trying out some try catch logic but doesn't seem to work as expected.

app.get("/tasks/:id", async (req, res) => {
  try {
    const _id = req.params.id;
    const task = await Task.findById(_id);

    if (!task) {
      return res.status(404).send("task not found");
    }
    res.send(task);
  } catch (error) {
    res.status(500).send("Internal server error");
  }
});

from this code sample, I'm making a query to Mongo DB to fetch some task but the problem is that if the task is not found, instead of running through the if statement, the program jumps directly to the catch block hence the if condition is not checked thus resulting to a different error. How can I fix this issue?

express node.js mongodb try-catch javascript
2 Answers

This is simply how MongooseJS works - check their Promises documentation and you will see that if a document is not found, an error will be thrown. If you were not using await, the findById() documentation shows how an error is returned if it cannot be found:

// find adventure by id and execute
Adventure.findById(id, function (err, adventure) {});

You can simply modify your route to look like the following:

app.get("/tasks/:id", async (req, res) => {
  let task;

  try {
    task = await Task.findById(req.params.id);
  } catch (error) {
    return res.status(404).send("task not found");
  }

  /* perform other checks or actions here if desired */

  res.send(task);
});

This is a little more flexible if you want to perform other error-checking; task is declared first so it can be accessible outside the try/catch block, and a 404 error is thrown if the task does not exist.

You can also look at the exists method which will return true or false based on if the document exists, but since you need the actual result that does not make as much sense.

user_13071830

You don't indicate what Task is, but it appears that it is rejecting when it doesn't find anything, rather than returning a false value (which is what you seem to be expecting).

Given that, you should probably just handle the error that it is throwing with something like

} catch ( error ) {
  // Will need to adapt this if to something that identifies the error thrown by `getById`
  if ( error.message.includes( 'not found' ) ) {
    res.status( 404 ).send( 'task not found' );
  } else {
     res.status( 500 ).send( 'Internal server error' );
  }
}
user_34434540
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