promise-loops.js

//jslint: es6 true

var Promise = require('bluebird');

var Continue = {}; // unique
var again = _ => Continue;

var repeat = fn => Promise.try(fn, again)
  .then(val => val === Continue && repeat(fn) || val);


// Example 1

var flipCoin = probability => Math.random() < probability;

var pBlah = repeat(again =>
    Promise.delay(1000)
    .then(_ => console.log("Hello"))
    .then(_ => flipCoin(0.9) && again() 
                             || "blah"));

pBlah.then(console.log)
    

// Example 2 

var orEnd = _ => _;

var pipe = (source, destination) => 
  repeat(again => 
    source.read()
    .then(data => destination.write(data))
    .then(again, orEnd)

// Example 3

var sum = 0, stop = 10;

repeat(again => {
  if (sum < stop) 
    return Promise.delay(250)
      .then(_ => console.log(++sum))
      .then(again));
})
.then(_ => console.log("Done"))