CoinStats.js

var CoinStats = (function () {
    var coin_data;
    var debug_mode = false;
 
    function clog(message){
      if( debug_mode == true ){
        console.log(message);
      }
    }

    function _browser( url ){
      clog( "XMLHttpRequest is running" );
      var request = new XMLHttpRequest();  
      request.open('GET', url, false);   
      request.send(null);
      return request.responseText;
    }

    function _UrlFetchApp( url ){
      clog( "UrlFetchApp is running" );
      var response = UrlFetchApp.fetch( url );
      var data = response.getContentText();
      return data;
    }

    function detectAndFetch( url ){
      clog( "deciding which method gonna run UrlFetchApp or XMLHttpRequest" );
      if (typeof UrlFetchApp === "undefined" ) {
        return _browser(url);
      }else{
        return _UrlFetchApp(url);
      }
    }

    function fetchCoinStats() {
      var furl = "https://api.coinmarketcap.com/v1/ticker/?limit=250";
      clog( "fetching coin stats from " + furl );
      data = detectAndFetch( furl );
      clog( "data has fetched, converting to json " + data );
      json_data = JSON.parse(data);
      clog( "transforming array of coin stats to key value object" );
      coin_data = transformCoinData(json_data);
      clog( "returning coin stats in json symbol=>price format " + JSON.stringify(coin_data) );
    }

    function transformCoinData( json_data ){
      var result = json_data.reduce(function(map, obj) {
          map[obj.symbol] = obj.price_usd;
          return map;
      }, {});

      return result;
    }

    function getCoinData(){
        if ( !coin_data ) {
          clog( "coin_data has no value, calling fetchCoinStats" );
          fetchCoinStats();
        }
        return coin_data;
    }
 
    var public = {
        getCoinStats: function () {
          return getCoinData();
        },

        getCoinPrice: function ( name ){
          getCoinData();
          clog( "returning coin price for " + name );
          return coin_data[name];
        }
    };

    return public;
})();


CoinStats.getCoinPrice("BTC");