AngularJS: Applying a function to 2-way data binding with a reroll button (reloadRoute??)

AngularJS APP

I would like to understand how I can solve this issue of the infinite digest Loop, should I write a conditional?

The objective is to use angular's 2-way data binding, but I need to modify the output to sort the letters randomly.

My HTML:

                <div class="container-fluid phrase-container text-center">
                <!-- == User Phrase Input == -->
                <input type = "text" ng-model = "phrase.firstPhrase" placeholder="Please enter phrase"><br><br>
            </div>

                <div class="container-fluid anagram-container text-center">
                <!-- == Final anagram ==  -->
                Anagram: {{phrase.fullAnagram()}}
            </div>

My javascript:

   var app = angular.module("app", []);

   app.controller('mainController', function($scope) {
   $scope.main = {};
   $scope.main.title = "AnagramJS";

// Refresh Page acts as reroll button
$scope.reloadRoute = function() {
    $route.reload();
};

// Anagram Creation
$scope.phrase = {
    firstPhrase: "",
    fullAnagram: function() {
        var finalPhrase;
        finalPhrase = this.firstPhrase.split('').sort(function() {
            return 0.5 - Math.random()
        }).join('');

        return finalPhrase

    }
};
   });

Simple $watch on scope model seems to work fine, so you could use:

<input ng-model="word" type="text"/>
<p>
   {{anagram}}
</p>

And in js:

$scope.$watch('word', (newVal, oldVal) => {
if (newVal) {
  // set anagram to randomize
  $scope.anagram = newVal.split('').sort(function() {
    return 0.5 - Math.random()
  }).join('');
} else {
  // empty anagram if word is empty
  $scope.anagram = "";
}
});

You can check how it works in this fiddle: https://fiddle.jshell.net/pegla/kemrr0ka/4/

UPDATE:

There's no need to use routing for reroll button, you can simply create function and call it multiple times, I added one way of doing it in my latest fiddle:

https://fiddle.jshell.net/kemrr0ka/5/