handle exception in javascript

Question

consider this code:

async function outer() {
    const inner = async () => {
        throw "xxx";
    };
    inner();
}
async function f() {
    try {
        await outer();
    }
    catch (error) {
        console.log(error);
    }
}
f();

when I run the code with node: node myfile.js, I will get this exception:

node:internal/process/promises:245
          triggerUncaughtException(err, true /* fromPromise */);
          ^

[UnhandledPromiseRejection: 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(). The promise rejected with the reason "xxx".] {
  code: 'ERR_UNHANDLED_REJECTION'
}

How can I modify the f function, so it will actually handle the exception? I specifically don't want to modify outer as this is blackbox code for me and I don't want to attach some global handler. What I want to achieve is to just modify the f so it actually handles the exception. Is that possible?

node --version
v15.14.0

What have you tried so far to solve this on your own? -> How much research effort is expected of Stack Overflow users? — Andreas
– Andreas, Commented Jun 16, 2021 at 8:05

Quentin · Accepted Answer · 2021-06-16 08:04:13Z

2

The promise created by inner isn't tied, in any way, to the promise created by outer. outer will resolve before the promise created by inner does.

You need to await it.

async function outer() {
    const inner = async () => {
        throw "xxx";
    };
    await inner();
}
async function f() {
    try {
        await outer();
    }
    catch (error) {
        console.log(error);
    }
}
f();

I specifically don't want to modify outer as this is blackbox code for me

It is the only way. You can't fix a bug in outer without changing outer.

answered Jun 16, 2021 at 8:04

Quentin

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