Some pseudocode representing part of what Backbone.Collection.fetch() does.

backboneFetch.js

Backbone.Collection = {
  fetch: function() {
    var requestUrl;
    
    if (isAFunction(this.url)) {
      requestUrl = this.url();
    } else {
      requestUrl = this.url;
    }
    
    this.emptyArray(this.models);

    $.ajax({
      url: requestUrl,
      type: "GET",
      dataType: "json"
    }).done(function(results){
      // `results` will be a list of vanilla JSON objects
      // `this.model` will be something returned by Backbone.Model.extend()
      var ModelConstructor = this.model;
      
      _.each(results, function(result){
        var model = ModelConstructor(result);
        this.models.push(model);
        this.triggerEvent("add", model);
      });

      this.triggerEvent("sync");
    });
  }
}