fpf.js

const add = (a, b) => a + b
const adds = (...n) => n.reduce(add)

const mul = (a, b) => a * b
const muls = (...n) => n.reduce(mul)

const div = (a, b) => a / b
const divs = (...n) => n.reduce(div)

const mod = (a, b) => a % b
const mods = (...n) => n.reduce(mod)

const app = (f, n) => f(n)
const appFlip = (n, f) => app(f, n)

const flow = (...fns) => n => fns.reduce(appFlip, n)
const pipe = (n, ...fns) => flow(fns)(n)

const toInt = n => n | 0

const mul10 = (a) => mul(a, 10) 
const mod10 = (a) => mod(a, 10)
const div10 = (a) => div(a, 10)
// (a * 10) + b 
const mulWithAdd = (a, b) => pipe(a, mul10, a_ => add(a_, b))