Result: a, b, d, c.
Expected: a, b, c, d
const promises = []
console.log('a')
someFunc(promises)
Promise.allSettled(promises).then(() => console.log('d'))
function someFunc(promises) {
const promise = new Promise(resolve => setTimeout(() => {
console.log('b')
const promise2 = new Promise(resolve2 => setTimeout(() => {
console.log('c')
resolve2()
}, 3000))
promises.push(promise2)
resolve()
}, 3000))
promises.push(promise)
return promise
}While it'd be possible to patch it up by not pushing to an array, but instead having each Promise chain off of each other in someFunc...
console.log('a')
someFunc().then(() => console.log('d'))
function someFunc() {
return new Promise(resolve => setTimeout(() => {
console.log('b')
new Promise(resolve2 => setTimeout(() => {
console.log('c')
resolve2()
}, 3000))
.then(resolve);
}, 3000))
}A much more understandable version would promisify setTimeout to begin with instead of doing it every time.
const setTimeoutPromise = ms => new Promise(resolve => setTimeout(resolve, ms));
console.log('a')
someFunc().then(() => console.log('d'))
function someFunc() {
return setTimeoutPromise(3000)
.then(() => {
console.log('b');
return setTimeoutPromise(3000)
})
.then(() => {
console.log('c');
return setTimeoutPromise(3000)
});
}Which can be further simplified with await...
const setTimeoutPromise = ms => new Promise(resolve => setTimeout(resolve, ms));
console.log('a')
someFunc().then(() => console.log('d'))
async function someFunc() {
await setTimeoutPromise(3000);
console.log('b');
await setTimeoutPromise(3000);
console.log('c');
await setTimeoutPromise(3000);
}I know you may be confused on this question a lot. Here is the solution I found
const promises = []
const timeout = ms => {
const promise = new Promise(resolve => setTimeout(resolve, ms))
promises.push(promise)
return promise
}
const someFunc = () =>
timeout(1000).then(() => {
console.log('b')
timeout(1000).then(() => console.log('c'))
})
async function main() {
console.log('a')
someFunc()
let i = 0;
while (promises.length > i) {
i = promises.length
await Promise.allSettled(promises)
}
console.log('d')
}
main()The problem I really want to express is that the content of the function someFunc is not determined at compile time while I need to make sure that the function leave no side effect once executed.