无法捕获异步 function 引发的错误

Question

I was readingthis article. In the below code the async 'foo' function returns the result of the async 'waitAndMaybeReject' function.

I am unable to understand why the catch block in 'foo' function is not executed when 'waitAndMaybeReject' throws an error.

 async function waitAndMaybeReject() { await new Promise(r => setTimeout(r, 5000)); const isHeads = false; //const isHeads = true; if (isHeads) return 'yay'; throw Error('Boo;'); } async function foo() { try { return waitAndMaybeReject(); } catch (e) { return 'caught'; } } foo();

Answer 1

You need to await the waitAndMaybeReject() function in order to be able to catch the exception. As it is described in the article you refer to:

By returning waitAndMaybeReject(), we're deferring to its result, so our catch block never runs.

To make it simple, when you return waitAndMaybeReject() you don't wait for it to resolve/reject in the try... catch block.