Basic Promise vs. Observable

obs-vs-promise.js

const {Observable} = require('rxjs');

function makeObs(){

   const obs =  Observable.create(sub => {
       setTimeout(() => {
           sub.next(3);
       },500);
   });
  .
   obs = obs.flatMap(() => {
        return someOtherObservable()
   });
  
  return obs;

}



function promiseProvider(){

   const promise =  new Promise((resolve,reject) => {
       setTimeout(() => {
           resolve(3);
       },500);
   });
  .
   promise = promise.then(() => {
        return someOtherPromise()
   });
  
  return promise;

}