function loadData(url,onResponse){
  var xhr = new XMLHttpRequest();
  xhr.open("GET", url);
  xhr.onreadystatechange = function(){
    if(xhr.readyState === 4 && xhr.status === 200){
      var infoObj = JSON.parse(xhr.responseText);
      onResponse(infoObj);
      }
    }
  xhr.send();
}

function useRetrievedData(dataObj){
  var conversion = new CurrencyConv(dataObj, "NOK", "SEK");
}

function someshit(){
  loadData("http://example.com/currencies", useRetrievedData);

}



function CurrencyConv(data,from,to){
  this.from = from;
  this.to = to;
  this.rate = data[from][to];

  this.offlineUpdate = function(newTo){
    this.to = newTo;
    this.rate = data[this.from][this.to];
  };
  this.onlineUpdate = function(newTo){
    var self = this;
    loadData("http://example.com/currencies", function(dataObj){
      self.to = newTo;
      self.rate = dataObj[self.from][self.to];
    });
  };
}