improved environment management

web/index.html

@@ -33,11 +33,12 @@
 
   <title>Velocity</title>
   <link rel="manifest" href="manifest.json">
-  <script src="https://na.gateway.mastercard.com/static/checkout/checkout.min.js">
-  </script>
-  <!-- <script src="https://test-gateway.mastercard.com/static/checkout/checkout.min.js"></script> -->
   <script type="text/javascript">
     function configure(sessionID) {
+      if (typeof Checkout === 'undefined') {
+        throw new Error('Checkout SDK not loaded.');
+      }
+
       Checkout.configure({
         session: {
             id:  sessionID
@@ -46,6 +47,10 @@
     }
 
     function showEmbeddedPage() {
+      if (typeof Checkout === 'undefined') {
+        throw new Error('Checkout SDK not loaded.');
+      }
+
       Checkout.showEmbeddedPage('#embed-target');
     }
   </script>