in test.js, I have some callback that resolves "a" value. then further the "a" value is exported at the end of the file
//test.js
let fun = async ()=>{
let a
await setTimeout(()=>{a = 10}, 100)
return a
}
let a
fun().then(val=>{a=val})
export default a
when im trying to import a value in test1.js, im getting a as undefiner
test1.js
import a from './test.js'
console.log(a) //undefined
This should work
test.js
// this does what you attempted to do
// but actually works
let fun = async () => {
let a = await new Promise(r => setTimeout(r, 100, 10));
return a;
};
let a = await fun();
export default a;
test1.js
import a from './test.js'
console.log(a)
setTimeout() that already returns a promise. If you're using top level await it's got to already be a fairly modern version of nodejs.
setTimeout(). v16 was released in April 2021 so in either case, it's been available for awhile. I don't scour the release notes either, but do read a "what's new" summary of each new major MTS release which I find beneficial.let is lexically scoped to the nearest block, so you actually have two different variables named a that just happen to have the same name.
The solution would be to use top-level await to export a Promise, for example:
export default await Promise.resolve(10)
setTimeout() that returns a promise.
Promise.resolve() in this example, since the length of the delay doesn't really matter.Promise.resolve() or setTimeout() as the value can just be exported directly.Promise.resolve() already resolves asynchronously, so I don't see a practical difference for this example. Also, Node 14 is still supported for another 7 months, so my answer supports it.
await setTimeoutmakes no sense sincesetTimoutdoesn't return a Promise