YahooFinance.js

(function(global) {
    'use strict';

    var BaseUri = 'http://query.yahooapis.com/v1/public/yql';

    var DefaultParameters = {
        diagnostics: true,
        env: 'http://datatables.org/alltables.env'
    };

    function createQuery() {
        var args = Array.prototype.slice.call(arguments);
        var symbols = args.map(encodeURIComponent).join();

        return 'select * from yahoo.finance.quotes where symbol in ("' + symbols + '")';
    }

    function parseResponse(xml) {
        var $query = $(xml).find('query').first();
        var created = new Date($query.attr('yahoo:created'));
        var quotes = $query.find('quote').get();

        return quotes.map(function(quote) {
            var $quote = $(quote);
            return {
                symbol: $quote.attr('symbol'),
                lastTradePrice: parseFloat($quote.find('LastTradePriceOnly').text()),
                retrieved: created
            };
        });
    }

    var YahooFinance = {
        baseUri: BaseUri,
        defaultParameters: DefaultParameters,

        lookupSymbols: function() {
            var args = Array.prototype.slice.call(arguments);
            var params = $.extend({}, DefaultParameters, { q: createQuery(args) });

            return $.Deferred(function(dfd) {
                $.get(YahooFinance.baseUri, params)
                    .fail(dfd.reject)
                    .done(function(xmlDoc) { 
                        var quotes = parseResponse(xmlDoc);
                        dfd.resolve(quotes);
                    });
            });
        }
    };

})(this);