Unhandled rejection - Promise

Question

I am new to UnhandledRejection. The below method is supposed to throw exception and terminate flow but it doesn't.Please favour on resolving it either way

Case 1: Took value from promise as true and tried conditions.But it is bypassed and returns unhandled rejection with the exception to be thrown.

Utils.isMaximumLimitReached(id).then(isLimit=>{
    console.log(isLimit); //true
    if(isLimit){
       throw "not allowed";
    }
  })

Edit: Case 3:This too returns Unhandled rejection this is not allowed

const isMaximumLimitReached = coachingId => {
  return db.coachingClassEntries
    .findAndCountAll()
    .then(counts => {
      let numberOfEntries = 2;
      //let maxEntries = counts.rows[0].coachingClass.maxEntries;
      let maxEntries=2;
      return new Promise((resolve,reject)=>{
        if (numberOfEntries == maxEntries) {
           reject('this is not allowed');
      }
      });

    });
};

  Utils.isMaximumLimitReached(data.coachingClassId).then().catch(error=>{
       throw error;
   })

Check This https://stackoverflow.com/questions/40500490/what-is-an-unhandled-promise-rejection . You need to add the catch block to handle every promise . — Rohan Kadu, Feb 16 '18 at 10:58
@RohanKadu even with catch block, it throws unhandled rejection — Gayathri, Feb 16 '18 at 11:25
In the last example you catch and rethrow. I guess what is calling `Utils.isMaximumLimitReached(data.coachingClassId).catch(()=>{...` isn't catching anything. — HMR, Feb 16 '18 at 11:50
@HMR Sorry. I corrected it now. EVen this returns unhandled rejection not allowed. — Gayathri, Feb 16 '18 at 12:18
Your second code sinippet doesn't seem to return the rejected promise at the `then` stage. — Redu, Feb 16 '18 at 12:23
@Redu second was unorderly. Please consider the present two . edited. — Gayathri, Feb 16 '18 at 12:27
The last code snippet still doesn't have a `reject` handler, you handle your error in the `resolve` handler. The syntax for `then` is like both answers given is like, with **two** functions as arguments. alternatively, you can change `.then` into `.catch`, which only needs a rejection handler. — Kevin Drost, Feb 16 '18 at 12:50
@KevinDrost I tried catch of reject too. It gives the same unhandled rejection — Gayathri, Feb 16 '18 at 12:58

score 1 · Answer 1 · answered Feb 16 '18 at 11:16

1

Promise rejections are usually handled with a second callback in the then method, which could look like this in your case 1:

Utils.isMaximumLimitReached(id).then(()=>{
  // everything is fine
}, (error) => {
  // promise was rejected, handle error
  console.log(error);
})

This way, any rejections caused by isMaximumLimitReached will be handled in the error callback.

answered Feb 16 '18 at 11:16

S.B.

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Case 3 is done as you suggested. I still get Unhandled rejection – Gayathri Feb 16 '18 at 12:20
@Gayathri where exactly is the unhandled rejection? If `findAndCountAll` is rejected, you also need to handle that as well. – S.B. Feb 16 '18 at 14:21
INSIDE isMaximumLimitReached , exactly in reject line – Gayathri Feb 16 '18 at 15:17

Rohan Kadu · Answer 2 · 2018-02-16T11:42:09.373

1

Change your Promise.reject with

Promise.reject(new Error('409',msg)).then(function() {
  // not called
}, function(error) {
  console.log(error); // Stacktrace
});

Hope this helps and resolve your issue. And If you want to throw the error then you check this before deciding what to use.

edited Feb 16 '18 at 11:42

answered Feb 16 '18 at 11:36

Rohan Kadu

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Could you please check case 3 and let me know what went wrong? – Gayathri Feb 16 '18 at 12:28

Unhandled rejection - Promise

2 Answers2