Reactive programming polling

poll_timer.js

const { from, timer } = require('rxjs');
const fetch = require('node-fetch');

const getTimeFromAPI = () => {
  return fetch('http://worldclockapi.com/api/json/est/now')
  .then((resp) => resp.json())
}


// Observer timer and subscribe
// emit first value after 1sec and subsequent values after every 3sec
timer(1000, 3000) // timer observable
.subscribe(
  _ => {
    // observe API and subscribe to it
    from(getTimeFromAPI()) // promise observable
    .subscribe((data) => {
      console.log('-------------------------------------------')
      console.log(data.currentFileTime)
    })
  }  
)