title: How to prefetch on a collection using Backbone
body: <p>I have the following method that performs a fetch on my collection and then calls the <code>render</code> function to display the results.  This all works fine and it's triggered every time the user gets down to the bottom of the page.  </p>
  
  <p>However during this fetch I then want to prefetch the next batch of items so that the experience will be better for the user.  I'm not sure how to achieve this.  I thought about doing another <code>this.collection.fetch</code> (Check my code) and then assigning the results to a variable but I wasn't sure if this is bad practice. </p>
  
  <p>Then I could maybe consult this variable to see if its got any contents the next time the user gets to the bottom of the page? </p>
  
  <p>Has anyone done something similar and can give me some guidance?</p>
  
  <pre><code>loadItems: function() {
  
      var that = this;
  
      this.collection.fetch({
          data: {"offset": this.offset, "limit": this.limit}, 
          success: function () {
              that.render();
  
              that.offset += that.limit;
  
              //Maybe I can do another fetch here
              this.collection.fetch({
                  data: {"skip": this.skip, "limit": this.limit, "sort": this.sortKey}
                  success: function () {
                      //However I'm not really sure how I would get the results and assign them to a variable
                  }
              });
          }
      });
  },
  render: function() {
      var self = this;
  
      _(this.collection.models).each(function(product){
          self.appendItem(product);
      }, this);
  },
  appendItem: function(product) {
      var productView = new ProductView({
          model: product
      });
      $(this.el).find(".products-list").append(productView.render().el);
  }
  </code></pre>