JS Bin// source https://jsbin.com/haxemip

jsbin.haxemip.js

var exchanges = [
  { 
    name: "NYSE",
    stocks: [
      { 
        symbol: "XFX", 
        closes: [
          { date: new Date(2014,11,24), price: 240.10 },
          { date: new Date(2014,11,23), price: 232.08 },
          { date: new Date(2014,11,22), price: 241.09 }
        ]
      },
      { 
        symbol: "TNZ", 
        closes: [
          { date: new Date(2014,11,24), price: 521.24 },
          { date: new Date(2014,11,23), price: 511.00 },
          { date: new Date(2014,11,22), price: 519.29 }     
        ]
      },
    ]
  },
  { 
    name: "TSX",
    stocks: [
      { 
        symbol: "JXJ", 
        closes: [
          { date: new Date(2014,11,24), price: 423.22 },
          { date: new Date(2014,11,23), price: 424.84 },
          { date: new Date(2014,11,22), price: 419.72 }
        ]
      },
      { 
        symbol: "NYN", 
        closes: [
          { date: new Date(2014,11,24), price: 16.82 },
          { date: new Date(2014,11,23), price: 16.12 },
          { date: new Date(2014,11,22), price: 15.77 }
        ]
      },
    ]
  }
];

Array.prototype.concatAll = function() {
  var results = [];
  
  this.forEach(function(subArray) {
    subArray.forEach(function(item) {
      results.push(item);
    });
  });
  
  return results;
};

Array.prototype.concatMap = function(projection) {
  return this.
    map(projection).
    concatAll();
};

//[1,2,3].map(function(num) { return num + 1; }) -> [2,3,4]
//[1,2].concatMap(function(num) { return [num + 1, num + 2]; }) -> [2,3,3,4]

var christmasEveCloses =
  exchanges.
    concatMap(function(exchange) {
      return exchange.stocks.
        concatMap(function(stock) {
          return stock.closes.
            filter(function(close) {
              return close.date.getMonth() === 11 &&
                close.date.getDate() === 24;
            }).
            map(function(close) {
              return {
                symbol: stock.symbol,
                price: close.price
              };            
            });
        });
    });

christmasEveCloses.forEach(function(christmasEveClose) {
  console.log(christmasEveClose);
});

Map Examples on multiple nested arrays