stuff.js

//-- Definition
Function.prototype.compose = function (/* ...args */) {
  var args = Array.prototype.slice.call(arguments)
    , funs = [ this ].concat(args)

  return function (/* ... */) {
    return funs.reduceRight(function (args, f) {
      return [ f.apply(null, args) ]
    }, arguments)[0]
  }
}

//-- Usage
var add10 = function(x) { return x + 10 }
  , mul2  = function(x) { return x * 2 }
  , add4  = function(x) { return x + 4 }

var composed = add10.compose(mul2, add4)

console.log(composed(5))