Series future example

series-future.js

// mkFuture
// :: Any next
// -> Any prev
// -> Future next
let mkFuture = next => prev => Future((reject, resolve) => {
  
  console.log(`start: ${prev},${next}`);

  setTimeout(() => {
    console.log(`resolve: ${prev},${next}`)
    resolve(next);
  }, Math.random() * 1000);
   
});

let safeErr = x => console.error(`err : ${x}`);
let safeLog = x => console.log(`log : ${x}`);

// toSeries
// :: Future f, Any v
// -> Future
const toSeries = (f, v) => f.chain(mkFuture(v));

// series :: Future
const series = reduce(toSeries, Future.of(0), [1,2,3,4]);

series.fork(safeErr, safeLog);