JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://documentcloud.github.com/underscore/underscore-min.js"></script>
<script src="http://documentcloud.github.com/backbone/backbone-min.js"></script>

JavaScript

$(function() {
    var MyModel = Backbone.Model.extend({});
    var MyCollection = Backbone.Collection.extend({

        add: function() {
            // Keep a copy of models before adding
            var modelsBefore = this.models.slice(0);
            console.log('COPIED', modelsBefore, this.models);
            Backbone.Collection.prototype.add.apply(this, arguments);
        }
    });

    var model = new MyModel();
    var model2 = new MyModel();
    var coll = new MyCollection();

    coll.add(model);
    coll.add(model2);
});