code: function processQueue() {
          var queue = nextTick.queue;
          var digest = nextTick.digest;
  
          nextTick.queue = [];
          nextTick.timeout = null;
          nextTick.digest = false;
  
          queue.forEach(function(queueItem) {
            var skip = queueItem.scope && queueItem.scope.$$destroyed;
            if (!skip) {
              queueItem.callback();
            }
          });
  
          if (digest) $rootScope.$digest();
        }
docs: Grab a copy of the current queue
  Clear the queue for future use
  Process the existing queue
  Trigger digest if necessary