Why unhandled promise rejection

Question

Wherever I am making a post request using postman to localhost:5000/api/profile/experience I am getting these warning

UnhandledPromiseRejectionWarning: ValidationError: Profile validation failed: experience.0.title: Path `title` is required., experience.0.company: Path `company` is required., experience.0.from: Path `from` is required.

and also I am not getting error message saying that title, company, from values are required eventhough I have not field those field. Here my validation js file

const Validator = require('validator');
const isEmpty = require('./is-empty');


module.exports = function validateExperienceInput(data){
    let errors = {};


    data.title = !isEmpty(data.title) ? data.title : '';
    data.company = !isEmpty(data.company) ? data.company : '';
    data.from = !isEmpty(data.from) ? data.from : '';


    if(Validator.isEmpty(data.title)){
        errors.title = 'Title field is required'
    }


    if(Validator.isEmpty(data.company)){
        errors.company = 'company field is required'
    }



    if(Validator.isEmpty(data.from)){
        errors.from = 'From field is required'
    }

return {
        errors, 
        isValid: isEmpty(errors)
    }
}

Here is the router file

router.post('/experience', passport.authenticate('jwt',{session: false}), (req,res) => {

    const {errors, isValid} = validateExperienceInput(req.body);

    Profile.findOne({user:req.user.id})
            .then(profile => {
                const newExp = {
                    title: req.body.title,
                    company: req.body.company,
                    location: req.body.location,
                    from: req.body.from,
                    to: req.body.to,
                    current: req.body.current,
                    description: req.body.description
                }

                // Add to exp array 

                profile.experience.unshift(newExp)
                profile.save().then(profile => res.json(profile))
            })
})

What am I missing?

Answer 1

You need to add a catch() (rejection handler) to findOne() to handle any errors/rejections occurring from findOne() . From the Node.js Process documentation for unhandledrejection :

The 'unhandledRejection' event is emitted whenever a Promise is rejected and no error handler is attached to the promise within a turn of the event loop. When programming with Promises, exceptions are encapsulated as "rejected promises". Rejections can be caught and handled using promise.catch() and are propagated through a Promise chain. The 'unhandledRejection' event is useful for detecting and keeping track of promises that were rejected whose rejections have not yet been handled.

router.post(
  "/experience",
  passport.authenticate("jwt", { session: false }),
  (req, res) => {
    const { errors, isValid } = validateExperienceInput(req.body);

    Profile.findOne({ user: req.user.id })
      .then(profile => {
        const newExp = {
          title: req.body.title,
          company: req.body.company,
          location: req.body.location,
          from: req.body.from,
          to: req.body.to,
          current: req.body.current,
          description: req.body.description
        };

        // Add to exp array

        profile.experience.unshift(newExp);
        profile.save().then(profile => res.json(profile));
      })
      .catch(err => {
        // do something with error here such send error message or logging
        // res.json(err);
      });
  }
);

Basically add a catch() anytime you have a then() to handle any errors rejections.

Hopefully that helps!