<3 JS

add.js

const add = (a) => (b) => a + b;
const addMore = (a) => (b) => (c) => add(a)(b) + c;

console.log(add(2)(4));
console.log(addMore(2)(4)(6));
// 6
// 12

trace.js

const pipe = (...fns) => x => fns.reduce((y, f) => f(y), x);
const trace = label => value => {
  console.log(`${label}: ${value}`);
  return value;
};
const g = n => n + 1;
const f = n => n * 2;
const h = pipe(g, trace('after g'), f, trace('after f'));

h(20);
// after g: 21
// after f: 42