JSFiddle - React, Tailwind, and code Playground

HTML

<script src="//cdnjs.cloudflare.com/ajax/libs/moment.js/2.5.0/moment.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/underscore.js/1.5.2/underscore-min.js"></script>
<script src="http://backbonejs.org/backbone.js"></script>
<!-- <script src="http://backbonejs.org/backbone.js"></script> -->
<div id="log">
</div>

JavaScript

$(document).ready(function () {
    ReportListItem = Backbone.Model.extend({        
        defaults: function () {
            return {
                "modificationDate": null
            }
        }
    })
    
    MyCollection = Backbone.Collection.extend({
        sortField: "modificationDate",
        descending: true,
        model: ReportListItem,
        comparator: function (a, b) {
            var value1 = a.get(this.sortField)
            var value2 = b.get(this.sortField)
            
            // date needs to be parsed before usage
            if (this.sortField === "modificationDate") {
                value1 = moment(value1)
                value2 = moment(value2)
                
                if (this.descending) {
                    if(value1.isBefore(value2))
                        return -1
                    else if(value1.isAfter(value2))
                        return 1
                    else
                        return 0
                }
                
                if (value1.isAfter(value2))
                    return 1
                else if (value1.isBefore(value2))
                    return -1
                else
                    return 0
                }
            
            if (this.descending) {
                return value1 > value2 ? -1
                : value1 < value2 ? 1
                : 0
            }
            
            return value1 > value2 ? 1
            : value1 < value2 ? -1
            : 0
        }
    })
    
    var item1 = new ReportListItem({ modificationDate: new Date(1389174631000) } )
    var item2 = new ReportListItem({ modificationDate: new Date(1389121649000) } )
    var item3 = new ReportListItem({ modificationDate: new Date(1389118794000) } )
    var item4 = new ReportListItem({ modificationDate: new Date(1388683574000) } )
    var item5 = new ReportListItem({ modificationDate: new Date(1388499055000) } )
    
    var collection = new MyCollection()
   ...