Either monad countdown timer. Requires monet.js

fp-monad-either.js

'use strict';


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


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


countdown({ time: 30 });