How to promisify ui-router state changes

sample.js

// create the deferred variable
var stateChanged = $q.defer();

// hook our functionality to its promise
stateChanged
  .promise
  .then(function () {
    // scroll to the desired element via ngSmoothScroll
    var element = document.getElementById(next);
    smoothScroll(element);
  });

// if we're on the desired state, just resolve the variable
if ($state.is('somewhere')) {
  stateChanged.resolve();
  return;
}

// otherwise go to the state 
$state.go('somewhere');

// hook to success for resolve
$rootScope.$on('$stateChangeSuccess', function () {
  // anonymous function is required, due to adding it inline causes errors
  stateChanged.resolve();
});

// hook to error for reject
$rootScope.$on('$stateChangeError', function () {
  // anonymous function is required, due to adding it inline causes errors
  stateChanged.reject();
});

The code is used for my article here: https://akosresch.wordpress.com/2016/01/27/how-to-promisify-ui-router-state-changes/