getting globalish things down (event source, session) into components - without breaking unit testing

backbone-modularity.js

// overall idea is to use prototype props
// to give access to shared instances of 
// 'globalish' stuff like session/router,
// but without resorting to globals. If we
// used straight globals, we couldn't have
// half the app using a different instance
// which might be necessary in future and is
// certaintly necess in testing

// so from use-case to implementation:

function bootApp() {
  var router = new AppRouter();
  var session = new Session();
  
  // plug in our top level deps
  View.setDependencies({router: router, session: session});
}

function testSomeView() {
  var instance = new View({
    session: {
      // mocking/stubbing still very
      // easy and predictable, rather
      // than globals which can't be per-instance
      login: function() {}
    }
  })
}

// here's how it works

var View = Backbone.View.extend({
  constructor: function(opts) {
    // allows for per-instance session/router
    _.extend(this,_.pick(opts,"session","router"));
    return Backbone.View.call(this,opts); // might be more fiddle, but you get the idea: `super()`
  },
  createChild: function(constructor,opts) {
    // cuts down on the boiler-plate required for passing down instance specific
    // session/router etc
    return new constructor(_.defaults(opts,{
      session: this.session,
      router: this.router
    }))
  }
},{
  setDependencies: function(opts) {
    // used to set app level instances
    _.extend(View.prototype,opts);
  }
});