fun-es2015.js

let compose = (...fns) => x => fns.reverse().reduce((acc, f) => f(acc), x);

let map = f => x => x.map(f);

let log = function() {
  console.log(this);
  return this;
};

let toUpperCase = x => x.toUpperCase();
let head = x => x[0];
let initials = compose(s => s.join('. '), map(compose(toUpperCase, head)), x => x.split(' '));
initials("hunter stockton thompson")::log(); // => H. S. T.

fun-es5.js

'use strict';

var _context;

var compose = function compose() {
  for (var _len = arguments.length, fns = Array(_len), _key = 0; _key < _len; _key++) {
    fns[_key] = arguments[_key];
  }

  return function (x) {
    return fns.reverse().reduce(function (acc, f) {
      return f(acc);
    }, x);
  };
};

var map = function map(f) {
  return function (x) {
    return x.map(f);
  };
};

var log = function log() {
  console.log(this);
  return this;
};

var toUpperCase = function toUpperCase(x) {
  return x.toUpperCase();
};
var head = function head(x) {
  return x[0];
};
var initials = compose(function (s) {
  return s.join('. ');
}, map(compose(toUpperCase, head)), function (x) {
  return x.split(' ');
});
(_context = initials("hunter stockton thompson"), log).call(_context);