Javascript Backbone.js-如何将3个模型组合成1个集合并输出所有数据？

我正在为我的项目（）使用jquery、backbonejs、下划线JS和Bootstrap3。这是我的源代码

我的问题是，如何在OrderCollections中将3个模型组合成1个集合

CategoryModel.js

define([
  'underscore',
  'backbone',
], function(_, Backbone) {

  var CategoryModel = Backbone.Model.extend({});

  return CategoryModel;

});

MerchantModel.js

define([
  'underscore',
  'backbone',
], function(_, Backbone) {

  var MerchantModel = Backbone.Model.extend({});

  return MerchantModel;

});

ProductModel.js

define([
  'underscore',
  'backbone',
], function(_, Backbone) {

  var ProductModel = Backbone.Model.extend({});

  return ProductModel;

});

OrderCollection.js

define([
  'underscore',
  'backbone',
  'models/category/CategoryModel',
  'models/merchant/MerchantModel',
  'models/product/ProductModel'
], function(_, Backbone, CategoryModel, MerchantModel, ProductModel){

 //stuck here
  var OrderCollection = Backbone.Collection.extend({
    model: CategoryModel,
    url:"https://izify.com/api/izify-api/user/get_all_categories.php",
    parse: function(data) {
        return data.tbl_categories;
    },

  });

  return OrderCollection;

});

然后，如何将所有数据检索到一个html页面中

OrderView.js

define(['jquery', 'underscore', 'backbone', 'models/global/GlobalModel', 'collections/order/OrderCollection', 'views/header/HeaderView', 'views/sidebar/SidebarView', 'views/footer/FooterView', 'text!templates/category/orderTemplate.html'], function($, _, Backbone, GlobalModel, OrderCollection,HeaderView,SidebarView,FooterView, orderTemplate) {
    var OrderView = Backbone.View.extend({
        el: $("#page"),
        initialize: function() {
            this.$el.off();
        },
        render: function(productId) {

            var that = this;
            var global = new GlobalModel();
            this.collection = new OrderCollection();
            var formValues = {
                merchantId: global.merchantId,
                productId: productId
            };
            this.collection.fetch({
                 data: formValues,
                success: function(collection, response) {
                    var template = _.template(orderTemplate, {
                        orders: that.collection.models
                    });
                    that.$el.html(template);
                    var sidebarView = new SidebarView();
                    sidebarView.render();
                },
                error: function(collection, response) {
                    console.log("error");
                }
            });
        },
    });
    return OrderView;
});

演示：

资源：

---

非常感谢。

创建不同模型集合的

魔力在于实现
模型
功能

下面是来自

你能根据我的问题详细解释一下吗？
var Library = Backbone.Collection.extend({

  model: function(attrs, options) {
    if (condition) {
      return new PublicDocument(attrs, options);
    } else {
      return new PrivateDocument(attrs, options);
    }
  }
});