This is the code from Monads - episode #21 of FunFunFunction (https://www.youtube.com/playlist?list=PL0zVEGEvSaeFSwPn06GKArptSxiP1Gff8)

monad-stream-example.js

const fetch = require('node-fetch')
const Bacon = require('baconjs')

function getInPortuguese(word) {
  // Google Translate API is a paid (but dirt cheap) service. This is my key
  // and will be disabled by the time the video is out. To generate your own,
  // go here: https://cloud.google.com/translate/v2/getting_started
  const apiKey =
    'AIzaSyB4DyRHIsNhogQXmH16YKbZfR-lTXrQpq0'
	const url =
    'https://www.googleapis.com' +
    '/language/translate/v2' +
  	'?key=' + apiKey +
    '&source=en' +
    '&target=pt' +
    '&q=' + encodeURIComponent(word)
  const promise = fetch(url)
 		.then(response => response.json())
	  .then(parsedResponse =>
    	parsedResponse
      	.data
        .translations[0]
        .translatedText
    )
  const stream = Bacon.fromPromise(promise)
  return stream
}

const stream = new Bacon.Bus()

stream
  .flatMap(word => getInPortuguese(word))
  .map(word => word.toUpperCase())
  .onValue(word => console.log(word))

stream.push('cat')
stream.push('meal')
stream.push('trumpet')

// Output of running this file will be:
// TROMBETA
// REFEIÇÃO
// GATO

Why don't you use simply

...
stream
  .flatMap(getInPortuguese)
  .map(word => word.toUpperCase())
  .onValue(console.log)
...

?

@Em-Ant Why not use this ? :)

...
stream
  .flatMap(getInPortuguese)
  .map(String.prototype.toUpperCase.apply)
  .onValue(console.log)
...

For learning purpose, I am using this code, without the need of setting up Google Translate API 😉

const portuguese = ['que', 'bonito', 'rir', 'pequeno', 'longe'];
const randomWord = arr => arr[Math.floor(Math.random() * (arr.length - 1))];
const getPortuguese = word => {
    const promise = Promise.resolve(`${word} ${randomWord(portuguese)}`);
    const stream = Bacon.fromPromise(promise);
    return stream;
};

Output using map():

Bacon.fromPromise({})
Bacon.fromPromise({})
Bacon.fromPromise({})

Output using flatMap():

CAT RIR
MEAL QUE
TRUMPET BONITO

FunFunFunction!