run promises sequentially or not using observables

observables.ts

import * as O from 'rxjs';

const delay = ms => new Promise((resolve) => setTimeout(() => resolve(ms), ms));

O.from([1,2,3])
  .pipe(
    O.map(x => O.defer(() => delay(1000))),
    O.mergeAll(1)
).subscribe(x => console.log(x))


console.log('done')



// allows grouiping / batching by count
import * as O from 'rxjs';

console.log('hi') //?

const delay = (ms, value) =>
  new Promise((resolve) => setTimeout(() => resolve(value), ms));

O.from([1,2,3, 4, 5, 6, 7, 8, 9 , 10])
  .pipe(
    O.bufferCount(3),
    O.map(x => O.defer(() => delay(1000, x))),
    O.mergeAll(1)
).subscribe(x => console.log(x))


console.log('done')

This will execute promises with concurrency passed to mergeAll