Version of Either monad(https://gist.github.com/o0/d517fbedd73ee759cb3beaf7574bd048) without external requirements on ES2015 Promises

fp-monad-either-promise.js

'use strict';


const tick = level => level.time === 1 ?
    Promise.reject(`Time's up`) :
    Promise.resolve(Object.assign({}, level, { time: level.time - 1 }));


const countdown = (level) => {
  console.info(level.time);
  setTimeout(() => tick(level).then(countdown, console.error), 1000);
};


countdown({ time: 5 });