Why is the catch statement inside the code not catching the error in async function?

Question

I have a .then in a promise return, and in that I have defined an async function that gets some data from an API. The part where I am stuck is that when I throw an error (Forcefully), it is not caught by the catch block.

From what I have learnt, a single .catch is enough for all the .then statements. Is this because there's another async function inside the code and hence the .catch is not working?

CampaignController.getOnboardingCampaignList = (req,res) => {

    return OnBoardingCampaign.find({description : {$exists : true}},{name: 1, description : 1, suggestedHaikuIds : 1})
    .then((r) => {
      // Some Logic here, unrelated the the work done below

        async function getSuggestedHaiku(){
            for(const campaign of r ){
                let suggestedHaikuIds = [];
                campaign.suggestedHaikus = [];
                throw new Error; // Using this to throw the new error
                if(campaign.suggestedHaikuIds === '') campaign.suggestedHaikuIds = [];
                else{
                    campaign.suggestedHaikuIds.forEach((id) => {
                        suggestedHaikuIds.push(Helper.parseId(id))
                    }) // This particular line threw the error initially
                    const result = await SuggestedHaiku.find({_id: {$in : suggestedHaikuIds}},{timeStamp : 0, deleted : 0, returnCount : 0, writtenCount : 0});

                    campaign.suggestedHaikus = result;
                }

            }

            if(r.length === 0){
                return Promise.reject(1001);
            }else{
                let result = {};
                result.list = r;
                Helper.success(res,"Onboarding Campaign List",result);
            }
        }
        getSuggestedHaiku();    


    })
    .catch(err => Helper.error(res, err)) // This catch did not catch the error thrown above

}

The error messages are as follows

UnhandledPromiseRejectionWarning: Error at getSuggestedHaiku (/Users/abhinav/haikuserver/controllers/campaign.js:242:23) at OnBoardingCampaign.find.then (/Users/abhinav/haikuserver/controllers/campaign.js:263:9) at process._tickCallback (internal/process/next_tick.js:68:7) warning.js:18 (node:7646) 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(). (rejection id: 2) warning.js:18 (node:7646) [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.

if you return getSuggestedHaiku(); it will - because Promises work that way — Jaromanda X
You're mixing promises with async/await. It makes the code less readable and harder to maintain. Advice: choose one way and stick with it! — Nir Alfasi
@JaromandaX Your solution works, could you please point me out to a resource from where I can learn more about it. — Clarskon

RIYAJ KHAN RIYAJ KHAN · Accepted Answer · 2019-06-19T05:48:08

Try catch should be wrapped to for loop.

try{

      for(const campaign of r ){}

}catch() {}

Why is the catch statement inside the code not catching the error in async function?

2 Answers