UnhandledPromiseRejection despite catching expection

Question

In the following code

// file: main.js
    class A {
    
        async start() {
            
            throw 'error';
        }
    }
    
    module.exports = A;



// file index.js

    var r = require('./main.js'); 
    
    let v = new r();
    
    try {
        v.start(); // error is caught when I use r.start() though
    } catch (e) {
        console.error(e);
    }

I am new to Javascript and Node.js, Node.js throws UnhandledPromiseRejection when I am clearly catching the exception, why does it happen ?

An `async` function always returns a promise which is **asynchronous**. Suggest you do some research into how to catch promise errors — charlietfl, Feb 15 '21 at 13:53
@charlietfl thanks for pointing it out, I added await and it worked, but just curious it works without await when I directly invoke it without creating an instance, why ?For ref, see the edited code — Ajay Sabarish, Feb 15 '21 at 14:30

score 0 · Answer 1 · answered Feb 15 '21 at 13:47

0

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

To see the reason:

node --trace-warnings index.js

answered Feb 15 '21 at 13:47

ManuelMB

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score 0 · Answer 2 · answered Apr 21 '23 at 11:03

Your code doesn't work, because you have to await for v.start()

This will work:

class A {
  async start() {
    throw 'error';
  }
}


(async() => {
  let v = new A();

  try {
    await v.start();
  } catch (e) {
    console.error(e);
  }
})()

But this won't

class A {
  async start() {
    throw 'error';
  }
}


(async() => {
  let v = new A();

  try {
    v.start();
  } catch (e) {
    console.error(e);
  }
})()

UnhandledPromiseRejection despite catching expection

2 Answers2

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