tienda_ilusion/don_confiao/static/js/add_line.js

@@ -1,7 +1,7 @@
 document.addEventListener('DOMContentLoaded', function(){
   var button = document.getElementById('add_line');
   var formContainer = document.getElementById('formset-container');
-  var totalForms = document.getElementById('id_form-TOTAL_FORMS');
+  var totalForms = document.getElementById('id_saleline_set-TOTAL_FORMS');
   button.addEventListener('click', function(){
     // Clonar un formulario vacío
     var newForm = formContainer.querySelector('.form-container').cloneNode(true);

tienda_ilusion/don_confiao/templates/don_confiao/purchase.html

@@ -13,7 +13,7 @@
       </div>
     {% endfor %}
   </div>
-  <button id="add_line">Añadir Linea</button>
+  <button id="add_line" type="button" onclick="add_line">Añadir Linea</button>
   <br/><button name="form" type="submit" >Comprar</button>
   <script src="{% static 'js/add_line.js' %}"></script>
 </form>