http://www.amazon.co.jp/dp/4798043761 にあるコードの一部(nodeで動かす)

gistfile1.js

#! /usr/bin/env node
// 2つの数をたす
var plus = function(a,b)
{
  return a + b;
};

// 2つの数を掛ける
var multiply = function(a,b)
{
  return a * b;
};

// 標準だとこう
// var s = [0,1,2,3,4,5,6,7,8,9].reduce(plus);
// console.log(s);

// reduceを再定義
var reduce = function(array, f){
  var s;
  for (var n = 0; n < array.length; n++){
    if (n==0)
      s = array[0];
    else
      s = f(s,array[n]); // ここでfを使う

    console.info('----------');
    console.info('n=', n);
    console.info('array[n]=', array[n]);
    console.info('s=', s);

  }
  return s;
};

// var after1 = reduce([0,1,2,3,4,5,6,7,8,9], plus);
// var after2 = reduce([1,2,3,4], multiply);

// mapを再定義
var map = function(array, f)
{
  var array1 = [];
  for (var n = 0; n < array.length; n++){
    array1[n] = f(array[n]); // fを使う

    console.info('----------');
    console.info('n=', n);
    console.info('array[n]=', array[n]);
    console.info('array1[n]=', array1[n]);
    console.info('array1=', array1);
  }
  return array1;
}
// 2倍にする
var double = function(x)
{
  return x * 2;
};
var after3 = map([0,1,2,3,4,5,6,7,8,9], double);

// 1足す
var increment = function(x)
{
  return x + 1;
};

var after4 = increment(5);
console.info('----------');
console.log(after4);
// ２倍して足す
var double_increment = function(x)
{
  return increment(double(x));
}
var after5 = double_increment(5);
console.info('----------');
console.log(after5 );

// 足して２倍
var increment_double = function(x)
{
  return double(increment(x));
}
var after6 = increment_double(5);
console.info('----------');
console.log(after6  );

// f は1足す gは2倍する
var f = increment;
var g = double;

/**
 * ひとつひとつかいていくならこう
 */
/**
var fg = function(x)
{
  return g(f(x));
};

var gf = function(x)
{
  return f(g(x));
};

var ff = function(x)
{
  return f(f(x));
};

var gg = function(x)
{
  return g(g(x));
};

console.info('----------');
console.log(f(5));
console.log(g(5));
console.log(fg(5));
console.log(gf(5));
console.log(ff(5));
console.log(gg(5));
**/

// 2つの関数を順に実行した関数を返す
var compose = function(f, g)
{
  var fg = function(x)
  {
    return g(f(x));
  };
  return fg;
};

var fg = compose(f, g);
var gf = compose(g, f);
var ff = compose(f, f);
var gg = compose(g, g);
console.info('----------');
console.log(f(5));
console.log(g(5));
console.log(fg(5));
console.log(gf(5));
console.log(ff(5));
console.log(gg(5));

var fggf = compose(fg, gf);
console.info('----------');
console.log(fggf(5));

//rangeの再定義
var range = function(n)
{
  var array = [];
  for (var i = 0; i < n; i++){
    array[i] = i;
  }
  return array;
};

console.info('----------');
console.log(range(10));

// 奇数を求める
var even = function(x)
{
  return x * 2 + 1;
};

var after7 = map(range(10), even);
console.info('----------');
console.log(after7);

var after8 = reduce(range(10), plus);
console.info('----------');
console.log(after8);

var after9 = reduce(range(1000), plus);
console.info('----------');
console.log(after9);