rx-from-async-iterator

A method to convert AsyncGeneratorObject to Rx.Observable

Install

npm i -S rx-from-async-iterator

Example

Simple usage

1import { fromAsyncIterator } from 'rx-from-async-iterator';
2import { fromEvent } from 'rxjs';
3import { take } from 'rxjs/operators';
4
5const click$ = fromEvent('click', document.body).pipe(take(2));
6
7async function sleepOneSecond() {
8  return new Promise(r => setTimeout(r, 1000));
9}
10
11async function* subTask() {
12  await sleepOneSecond();
13  yield "d";
14  await sleepOneSecond();
15  yield "e";
16  await sleepOneSecond();
17}
18
19async function* taskAsync(error?: Error) {
20  yield "a";
21  await sleepOneSecond();
22  yield "b";
23  await sleepOneSecond();
24  yield "c";
25  yield* subTask();
26  yield "f";
27  yield click$;
28}
29
30fromAsyncIterator(taskAsync()).subscribe(console.log);
31/// output as follows:
32// -> 'a'
33// -> 'b'
34// -> 'c'
35// -> 'd'
36// -> 'e'
37// -> 'f'  /// and one second duration between each letter.
38// -> MouseEvent
39// -> MouseEvent

Real world example

Imagine we have an QRCode sign up feature to do, we need to poll an backend interface called /check/login

1async function* pollCheckLogin() {
2  let currentStatus = 'currentStatus';
3	while(currentStatus === 'pending') {
4    yield currentStatus = (await fetch('/check/login').then(resp => resp.json)).status;
5  }
6  if (currentStatus === 'timeout') {
7		yield 'timeout';
8  }
9  if (currentStatus === 'success') {
10    yield 'login success';
11    return;
12  }
13	throw new Error('unknown status');
14}
15
16fromAsyncIterator(pollCheckLogin()).subscribe((status) => {
17  switch(status) {
18    case 'timeout':
19      // handle timeout
20      break;
21    case 'login success':
22      // go to home page
23      break;
24    case 'pending':
25      // handle pending
26      break;
27  }
28});

Try it