UnhandledPromiseRejectionWarning: This error originated either by throwing inside of an async function without a catch block

Question

I am getting following error in my Node-Express App

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: 4)

To say the least, I have created a helper function which looks something like this

const getEmails = (userID, targettedEndpoint, headerAccessToken) => {     return axios.get(base_url + userID + targettedEndpoint,  { headers: {"Authorization" : `Bearer ${headerAccessToken}`} })     .catch(error => { throw error}) } 

and then I am importing this helper function

const gmaiLHelper = require("./../helper/gmail_helper") 

and calling it inside my api route like this

router.get("/emailfetch", authCheck, async (req, res) => {   //listing messages in users mailbox    let emailFetch = await gmaiLHelper.getEmails(req.user._doc.profile_id , '/messages', req.user.accessToken)   .catch(error => { throw error})   emailFetch = emailFetch.data   res.send(emailFetch) }) 

From my end, I think I am handling the error by using catch block.

Question: Can someone explain me why I am getting the error and how can I fix it?

Answer 1

.catch(error => { throw error}) is a no-op. It results in unhandled rejection in route handler.

As explained in this answer, Express doesn't support promises, all rejections should be handled manually:

router.get("/emailfetch", authCheck, async (req, res, next) => {   try {   //listing messages in users mailbox      let emailFetch = await gmaiLHelper.getEmails(req.user._doc.profile_id , '/messages', req.user.accessToken)     emailFetch = emailFetch.data     res.send(emailFetch)   } catch (err) {     next(err);   } }) 

Answer 2

I suggest removing the below code from getMails

 .catch(error => { throw error}) 

In your main function you should put await and related code in Try block and also add one catch block where you failure code.

---

you function gmaiLHelper.getEmails should return a promise which has reject and resolve in it.

Now while calling and using await put that in try catch block(remove the .catch) as below.

router.get("/emailfetch", authCheck, async (req, res) => {   //listing messages in users mailbox  try{   let emailFetch = await gmaiLHelper.getEmails(req.user._doc.profile_id , '/messages', req.user.accessToken) } catch (error) {   // your catch block code goes here })