ES5 and ES6 implementations of compose - readable implementation, not optimized

compose.es6.js

function compose(...fnArgs) {
  const [first, ...funcs] = fnArgs.reverse();
  return function(...args) {
    return funcs.reduce((res, fn) => fn(res), first(...args));
  };
}

compose.js

function compose() {
  var funcs = Array.prototype.slice.call(arguments).reverse(); // turn args into (reversed) array
  return function() {
    return funcs.slice(1).reduce(function(res, fn) {
      return fn(res);
    }, funcs[0].apply(undefined, arguments));
  }
}