gistfile1.js

var Page = {
  contextFetchers: {
  },
  runContextFetchers: function(eventName) {
    var contextFetchers = this.contextFetchers[eventName] || [];
    var context = this;
    var names = [];
    $.each(contextFetchers, function(idx, callback) {
      if($(names).filter(function(idx, obj){return callback.name == obj}).length !== 0) {
        return;
      }
      names.push(callback.name);
      var response = callback() || {};
      $.each(response, function(key, value) {
        context[key] = value;
      })
    });
  },
  registerContextFetcher: function(eventName, contextFetcher) {
    var fetchers = this.contextFetchers[eventName] || [];
    fetchers.push(contextFetcher);
    this.contextFetchers[eventName] = fetchers;
  }
};

var Page1 = {};
var Page2 = {};
$.extend(Page1, Page);
$.extend(Page2, Page);