Recurly.js submit coupon automatically

gistfile1.js

Recurly.buildSubscriptionForm({
   /* other options */
  subscription: {
          couponCode: 'testplan'
  },
  distinguishContactFromBillingInfo: true,
  afterInject: function(){                                                                                                              
          $('.submit').text('Join Playa');
          $('div.check').click();
  },
});