Some functional JS we like

functional.js

const pipe = (...fns) => x => fns.reduce((acc, fn) => fn(acc), x); //x = form

const curry = fn => (...args) => fn.bind(null, ...args);

const map = curry((fn, arr) => arr.map(fn));

const join = curry((str, arr) => arr.join(str));

const toLowerCase = str => str.toLowerCase();

const split = curry((splitOn, str) => str.split(splitOn));

const compose = (...fns) => x => fns.reduceRight((v, f) => f(v), x);




const tap = curry((fn, x) => {
  fn(x);
  return x;
});



const trace = curry((label, x) => {
  console.log(`== ${ label }:  ${ x }`);
  return x;
});

// or write it a a special tap
const trace = label => {
  return tap(x => console.log(`== ${ label }:  ${ x }`));
};

const toSlug = pipe(
  trace('input'),
  split(' '),
  map(toLowerCase),
  trace('after map'),
  join('-'),
  encodeURIComponent
);

console.log(toSlug('JS Cheerleader'));
// '== input:  JS Cheerleader'
// '== after map:  js,cheerleader'
// 'js-cheerleader'