I'm having an issue with JavaScript's async/await functions. This is happening on an internal application that I can't share the source for, but I put together a quick generic reproduction of my issue:
function sleep(ms) { return new Promise(resolve => setTimeout(resolve, ms)); } async function baz(input) { console.log("4"); await sleep(1000); console.log("5"); return input; } async function bar(input) { console.log("3"); return await baz(input); } async function foo() { console.log("2"); const foo = await bar("foo"); return foo; } console.log("1"); foo(); console.log("6");
I would expect this to return the following with a one second wait between 4
and 5
:
1
2
3
4
5
6
"foo"
Instead, after trying this in the console in Chrome 64.0.3282.167 and Firefox 58.0.2 I receive this:
1
2
3
4
6
undefined
5
Please can someone point out where I'm going wrong in this?
The top-level is running synchronously (as it always does) - it doesn't wait for foo();
to resolve before continuing to console.log("6");
. Wrap the calling of foo
in something async and await
it. You also need to save the return value of foo
if you want to display its later:
function sleep(ms) { return new Promise(resolve => setTimeout(resolve, ms)); } async function baz(input) { console.log("4"); await sleep(1000); console.log("5"); return input; } async function bar(input) { console.log("3"); return await baz(input); } async function foo() { console.log("2"); const foo = await bar("foo"); return foo; } (async () => { console.log("1"); const str = await foo(); console.log("6"); console.log(str); })();
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