respond_to js and json

respond_to.rb

module Admin
  class EcardProgramsController < BaseController
    def index
      @ecard_programs = EcardProgram.all
    end

    def create
      @ecard_program = EcardProgram.new(ecard_program_params)

      respond_to do |format|
        if !@ecard_program.save
          format.html { redirect_to admin_ecard_programs_path }
          format.js
        else
          format.js { render json: { success: false }, status: :unprocessable_entity}
        end
      end
    end

    private

    def ecard_program_params
      params.require(:ecard_program).permit(:name, :code)
    end
  end
end

== Getting this error in my browser ==

Uncaught SyntaxError: Unexpected token :
    at processResponse (rails-ujs.self-817d9a8cb641f7125060cb18fefada3f35339170767c4e003105f92d4c204e39.js?body=1:246)
    at rails-ujs.self-817d9a8cb641f7125060cb18fefada3f35339170767c4e003105f92d4c204e39.js?body=1:173
    at XMLHttpRequest.xhr.onreadystatechange (rails-ujs.self-817d9a8cb641f7125060cb18fefada3f35339170767c4e003105f92d4c204e39.js?body=1:230)