Flash message in AJAX rendering

I have a Products and product Reviews controller. Im trying to display a Flash message ("Your review is under review for approval") in my AJAX rendering when a review is created. Not sure how do i go about doing so.

Review Controller

def create
  @product = Product.find(params[:product_id])
  @review = Review.new(review_params)
  @review.user = current_user
  @review.product = @product
  respond_to do |format|
    if @review.save
      format.html { redirect_to product_path(@product), flash[:notice]="Your review is under review for approval" }
      format.js {render :create_success}
    else
      format.html { render "products/show" }
      format.js {render :create_failure}
    end
  end
end

create_success.js.erb

$("#reviews").prepend("<%= j render '/reviews/review', review: @review %>");
<% @review = Review.new %>
$("#new_review").replaceWith("<%= j render 'review_form' %>")

index.html.erb

<%= simple_form_for [@product, @review], remote: true do |f| %>
 <div class="form-group">
   <%= f.input :review_comment, placeholder: "Let us know what you think here..."%>
 </div> 
 <div>
   <%= f.submit "Submit", class: "btn mui-btn--raised pull-right review-form-btn", data: {disable_with: "Saving..."} %>
 </div>
<% end %>