app.js

var Backbone = require('backbone')
  , example = require('./routes/example.js')
  , _ = require('lodash');
  
var App = Backbone.router.extend({
  initialize: function () {
    this.route('example', _.bind(example, this))
  }
});

module.exports = App;

entry.js

var App = require('./app.js')
  , Backbone = require('backbone');

window.app = new App();
Backbone.history.start();

example.js

var example = function () {
  // your route
  /*
   *  also, `this` will be your `app`
   */
}

module.exports = example;