ES6 compose

compose.js

// both answers copied from challange posted at e-mail list of my former job

// not-so oneliner
var compose = function () {
    var composableFunctions = Array.prototype.slice.call(arguments).reverse();
    return (x) => composableFunctions.reduce((result, composable) => composable(result), x);
  /*
  ES5:
  return function(x) {
    return composableFunctions.reduce(function(result, composable) {
        return composable(result)
    }, x);
  }*/
}

// one-liner
var compose = (...fs) => (x) => fs.reduce((p,f) => f(p), x);
/*
ES5: 
var compose = function() {
    var fs = Array.prototype.slice.call(arguments);
    return function(x) {
        return fs.reduce(function(p, f) {
             return f(p);
        }, x);
    }
}
*/