gistfile1.js

// Lazily load models via XHR in MVC-style JavaScript

var Model = function(params) {};
Model.load_and_retry = function(id, controller, controller_variable) {
  var controller_method = this.load_and_retry.caller;
  var data_loaded_callback = function(data) {
    controller[controller_variable] = new Model(data);
    controller_method.apply(controller);
  };

  load_with_xhr("some/url/"+id+".json", data_loaded_callback);
};


// Example

var Controller = function() {};
Controller.prototype.do_something = function() {
  if(!this.my_model) {
    return Model.load_and_retry(this.model_id, this, "my_model");
  }
  alert(this.my_model);
}