// source http://jsbin.com/cisiju

rambaquiz.js

/*******************************************
               Y O U R  T U R N
********************************************/
var articles = [
  {
    author: {
      name: 'mike',
      email: 'mike@gmail.com'
    },
    books : [
      {
        title : 'java',
        price : 14000
      },
      {
        title : 'cpp',
        price : 16000
      }
    ]
  },
  {
    author: {
      name: 'peter',
      email: 'peter@outlook.com'
    },
    books : [
      {
        title : '.net',
        price : 20000
      },
      {
        title : 'python',
        price : 20000
      }
    ]
  },
];

// ----------------------------------------------------------
// 1. 저자의 이름만 가져오기
// ----------------------------------------------------------
// 1. for문 사용하기
var getAuthorName = function(array){
  var result = [];
  array.forEach(function(item1, index1, array1){
    result.push(item1.author.name);
  });
  return result;
};
console.log(getAuthorName(articles));

// 2. array의 map 사용
var getAuthor = function(obj){ return obj.author; };
var getName = function(obj){ return obj.name; };
var getAuthorName = function(obj) { return obj.map(getAuthor).map(getName); };
console.log(getAuthorName(articles));

// 3. rambda.js의 curry, map, compose 사용
var get = R.curry(function(x, obj){ return obj[x]; });
var getAuthorName = R.compose(R.map(get('name')), R.map(get('author')));
console.log(getAuthorName(articles));

// ----------------------------------------------------------
// 2. 저자의 책값의 총합을 가져오기
// ----------------------------------------------------------
// 1. for문 사용하기
var getBookTotalPrice = function(array){
  var result = [];
  array.forEach(function(item1, index1, array1){
    result[index1] = 0;
    item1.books.forEach(function(item2, index2, array2){
      result[index1] += item2.price;
    });
  });
  return result;
};
console.log(getBookTotalPrice(articles));

// 2. array의 map, reduce 사용
var getBook = function(obj){ return obj.books; };
var getTotalPrice = function(obj){ return obj.reduce(
  function(prev, now, index, array) { 
    return prev.price + now.price; 
  }); 
};
var getBookTotalPrice = function(obj) { return obj.map(getBook).map(getTotalPrice); };
console.log(getBookTotalPrice(articles));

// 3. ramba.js 사용
var get = R.curry(function(x, obj){ return obj[x]; });
var log = R.curry(console.log);

var getBookTotalPrice0 = R.compose(R.map(R.reduce(R.add, 0)), R.map(R.map(get('price'))), R.map(get('books')));
console.log(getBookTotalPrice0(articles));

var getBookTotalPrice1 = R.compose(R.map(R.sum), R.map(R.map(get('price'))), R.map(get('books')));
console.log(getBookTotalPrice1(articles));

var total = R.curry(function(x, obj){ return R.compose(R.sum, R.map(get(x)))(obj); });
var getBookTotalPrice2 = R.compose(R.map(total('price')), R.map(get('books')));
console.log(getBookTotalPrice2(articles));