diff --git a/example/src/main/assets/demo.html b/example/src/main/assets/demo.html
index c1dd3d1..dc358fc 100644
--- a/example/src/main/assets/demo.html
+++ b/example/src/main/assets/demo.html
@@ -94,16 +94,22 @@
                 var data = {
                     'Javascript Responds': '测试中文!'
                 };
-                console.log('JS responding with', data);
-                responseCallback(data);
+
+                if (responseCallback) {
+                    console.log('JS responding with', data);
+                    responseCallback(data);
+                }
             });
 
             bridge.registerHandler("functionInJs", function(data, responseCallback) {
                 document.getElementById("show").innerHTML = ("data from Java: = " + data);
-                var responseData = "Javascript Says Right back aka!";
-                responseCallback(responseData);
+                if (responseCallback) {
+                    var responseData = "Javascript Says Right back aka!";
+                    responseCallback(responseData);
+                }
             });
         })
     </script>
 
-</html>
\ No newline at end of file
+</html>
+