I have a function that returns a promise, and I am trying to await on it from within an async function. The problem is that the program completes immediately, instead of awaiting the promise.
async-test.js:
function doItSlow() {
const deferred = new Promise();
setTimeout( () => {
console.log( "resolving" );
deferred.resolve();
}, 1000 );
return deferred;
}
async function waitForIt( done ) {
console.log( "awaiting" );
await doItSlow();
console.log( "awaited" );
done();
}
waitForIt(() => {
console.log( "completed test" );
});
console.log( "passed by the test" );
Build and run:
babel --stage 0 --optional runtime async-test.js > at.js && node at.js`
Result:
awaiting
passed by the test
Resolving immediately instead of waiting one second has no effect:
function doItSlow() {
const deferred = new Promise();
console.log( "resolving" );
deferred.resolve();
return deferred;
}
Interestingly, "resolving" is never printed, even though it is now synchronous:
awaiting
passed by the test
I would suspect a compiler problem, but I checked Babel's output and sure enough, it did compile the synchronous version.
I thought I could just await on a promise from within an async function. Is there something I am missing here?
Answer
You are not using Promise
right (assuming it's standard compliant). It doesn't have resolve
method. You should pass a function instead:
function doItSlow() {
return new Promise(resolve => {
setTimeout( () => {
console.log( "resolving" );
resolve();
}, 1000 );
});
}
No comments:
Post a Comment