code: function addReview(reviews, review) {
    if (!reviews.length) {
      return [review];
    }
  
    var i = reviews.length - 1;
    for (; i >= 0; i -= 1) {
      if (reviews[i].ts <= review.ts) {
        break;
      }
    }
  
    var newReviews = reviews.slice(0);
    newReviews.splice(i + 1, 0, review);
  
    return newReviews;
  }
docs: This function only works if reviews is always sorted by timestamp