obs.js

const delay = require('delay')
async function* makeCountingObservable() {
  let count = 0
  while(true) {
    if (count > 4) return
    await delay(1000)
    yield count++
  }   
}
const counter = makeCountingObservable()

;(async function() {
  
  let lastIterat 
  while(true) {
    lastIterated = await counter.next()
    if (lastIterated.done) return
    console.log(lastIterated.value)
  }

  for await (const num of counter) {
    console.log(num)
  }
})()



const greetings = ['hej', 'oi', 'hello']
for(const greeting of greetings) {
  console.log(greeting)
}


function makeCountingStream() {
  let count = 0
  let handler = null
  setInterval(function() {
    count++
    handler(count)
  }, 500)

  return {
    each: function(callback) {
      handler = callback
    }
  }
}

const stream = makeCountingStream()
stream.each(function(message) {
  console.log(message)
})




function makeValueAfterOneSecondPromise() {
  
  return {
    then: function(callback) {
      setTimeout(function() {
        callback("hello")
      }, 1000)
    }
  }
}

const promise = makeValueAfterOneSecondPromise()
promise.then(function(message) {
  message //?
})