loop.js

const delay = (delay) => () => new Promise((resolve, reject) => setTimeout(resolve, delay))
const main = () => f1().then(f2).catch(f3)

const f1 = () =>  new Promise((resolve, reject) => ret ? resolve() : reject())
const f2 = () => Promise.resolve('f2')
const f3 = () => Promise.resolve('f3')

let ret = true
const next = () => ret = !ret

const loop = () => main().then(console.log).then(next).then(delay(1000)).then(loop)
loop()