chap3 -> Creating a binding to debug - the toJSON binding

ko-cart/index.html

@@ -19,6 +19,7 @@
             </div>
             <div data-bind="template: {name:'add-to-catalog-modal'}"></div>
             <div data-bind="template: {name:'finish-order-modal'}"></div>
+            <pre class="well well-lg" data-bind="toJSON: $root"></pre>
         </div>
 
         <!-- vendor library -->

ko-cart/js/custom/koBindings.js

@@ -23,3 +23,11 @@ ko.bindingHandlers.currency = {
     });
   },
 };
+
+ko.bindingHandlers.toJSON = {
+  update: function (element, valueAccessor) {
+    return ko.bindingHandlers.text.update(element, function () {
+      return ko.toJSON(valueAccessor(), null, 2);
+    });
+  },
+};