function assignWithRandomPriority_(attendees, activities, numActivitiesPerPerson) {
  let activitiesById = activities.reduce(function(obj, activity) {
    obj[activity.id] = activity;
    return obj;
  }, {});
  for (let i = 0; i < numActivitiesPerPerson; ++i) {
    let randomizedAttendees = shuffleArray_(attendees);
    randomizedAttendees.forEach(function(attendee) {
      makeChoice_(attendee, activitiesById);
    });
  }
}
Selects activities via random priority.

@param {object[]} attendees - Array of attendees to assign activities to
@param {object[]} activities - Array of all available activities
@param {number} numActivitiesPerPerson - Maximum number of activities to assign