my proposal for implementing feature flags client-side based on hard-coding a role (we could do a group too, i just used role because it was easy to show the idea).

dashboard-view.js

define([
  'feature-flags'
], function(feature) {
  // .. instantiate the view and all of that
  
  feature.promise().then(function() {
    path.map(url).to(function() {
      if (feature.flags.dashboard)
        view.show();
      });
  });
});

feature-flags.js

define([
  // this is currently the 'config/feature-flags.json' file,
  // and it would be something like `{production: true, staging: false}`
  'json!environment.json'
], function(environment) {
  var productRole = '4e6fa6187a475eefd68fb5f8';
  
  var object = {
    // this is what the widgets will use to access the flags
    flags: null,
    
    // deferring this makes it possible to involve an api call in the future
    promise: $.Deferred().then(function(flags) {
        // also export the flags to the viewmodel so view's templates can bind to them
        object.flags = viewmodel.features = flags;
      }).resolve({
        dashboard: !environment.production || waterfall.authenticate.role === productRole;
      }).promise();
  };
  
  return object;
});

navbar.js

define([
  './../three-widget',
  'feature-flags'
], function(ThreeWidget, feature) {
  var mapping = {
    defaults: {
      flags: {
        dashboard: false
      }
    }
  };
  
  $.widget('msgme_navbar', ThreeWidget, {
    _create: function() {
      // assume that the caller loaded the flags before instantiating this
      mapping.defaults.flags = feature.flags;
      ThreeWidget.prototype._create.apply(this, arguments);
    }
  });
});