CODEWITHSUNDEEP
javascriptnode.jsecmascript-6promise
patrickhuang94
patrickhuang94

Reputation: 2113

Unhandled promise rejection in Node.js

I'm trying to make a DELETE call and I'm implementing the function below. I understand that in a promise, there needs to be a "resolve" and a "reject" state, but I'm getting an unhandled promise rejection error:

UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): [object Object]

I don't really like using conditional statements inside a promise because it gets messy, but what I'm trying to do here is to check if the organization is verified, and if it is, a delete operation should not occur and will reject. 

function deleteOrg(id) {
    return new Promise((resolve, reject) => {
        // A helper function that returns an 'org' object
        findById(id)
        .then((orgObject) => {
            if (orgObject.verified_at !== null) {
                throw new Error(422, 'Unable to delete organization')
            }

            //Organization is not verified, so proceed to delete
            new Organization().where({'id': id}).destroy()
            .then(() => {
                return resolve() //return 200 upon deletion
            })
            .catch((err) => {
                return reject(new Error(500, 'Unable to delete organization'))
            })
        })
        .catch((err) => {
            const m = `Unable to delete organization: ${err.message}`
            return reject(new Error(500, m))
        })
    })
}

I'm pretty sure I'm handling the rejection inside the if wrong.

Upvotes: 3

Views: 3448

Answers (4)

Gurujegan
Gurujegan

Reputation: 11

I actually ran into the same kind of problem because I failed to add the return keyword to the calling method(deleteOrg(id)). After adding return UnhandledPromiseRejectionWarning gone away.

function deleteOrg(id)
{
// actually returns a promise 
}

return deleteOrg.then((result) => { 
   //code logic after deleting the record// 
});

Upvotes: 0

kbvishnu
kbvishnu

Reputation: 15630

original method() => {
             try{ //code to raise the exceptio


            })

;

The best way to handle is to use expect It can be matched with an exception. A sample test

  someMock.mockFunc(() => {
          throw new Error("Something");
        });

   test('MockFunc in error', () => {
     return expect(orginalCall()).rejects.toMatch('Something');
   });

Upvotes: 0

nem035
nem035

Reputation: 35481

Creating promises inside promise constructors is a known anti-pattern. Try modularizing your promises into separate functions instead:

function deleteOrg(id) {

  const verifyOrg = (orgObject) => {
    if (orgObject.verified_at !== null) {
      throw new Error(422, 'Unable to delete organization')
    }
  };

  const destroyOrg = () => new Organization().where({
    'id': id
  }).destroy();

  return findById(id)
    .then(verifyOrg)
    .then(destroyOrg);
}

Where you can let the errors propagate through the promise chain and handle them outside:

deleteOrg(id)
  .catch((err) => {
    const m = `Unable to delete organization: ${err.message}`;
    // ...
  });

Upvotes: 0

Jaromanda X
Jaromanda X

Reputation: 1

as findById and .destroy return Promises, there is no need for the Promsie constructor

Your code is then simplified to

function deleteOrg(id) {
    return findById(id)
    .then((orgObject) => {
        if (orgObject.verified_at !== null) {
            throw new Error(422, 'Unable to delete organization')
        }

        //Organization is not verified, so proceed to delete
        return new Organization().where({'id': id}).destroy()
        .catch((err) => {
            throw (new Error(500, `Unable to delete organization: ${err.message}`));
        });
    });    
}

Upvotes: 0

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