How to handle the unavailable properties of controllers on the page ?

Handle unavailable properties

Check the property for undefined value and show the message using ng-show



JS
app.controller("helloController", function ($scope) {
   $scope.helloMessage = "Hello";
       $scope.rootMessage = "Welcome";
});

HTML
<div ng-controller="helloController"> 
    Root message : {{ rootMessage }}  <br/>
    Hello message : {{ helloMessage }}  <br/>
    Bye message :
       <span style="color:red" ng-show="byeMessage == undefined">
           Bye message is undefined.
       </span>
</div>





Output
Root message : Welcome
Hello message : Hello
Bye message : Bye message is undefined.