AngularJS ng-change Directive
Example
Execute a function when the value of the input field changes:
    <body ng-app="myApp">
<div ng-controller="myCtrl">
    
    <input type="text" ng-change="myFunc()" ng-model="myValue" />
    
    <p>The input field has changed {{count}} times.</p>
</div>
    <script>
    angular.module('myApp', [])
.controller('myCtrl', ['$scope', 
    function($scope) {
    $scope.count = 0;
    
    $scope.myFunc = function() {
        
    $scope.count++;
    };
}]);
</script>
</body>
  
Try it Yourself »
Definition and Usage
The ng-change directive tells AngularJS what to do when the 
value of an HTML element changes.
The ng-change directive requires a ng-model 
directive to be present.
The ng-change directive from AngularJS will not override the element's original onchange event,
both the ng-change expression and the original onchange event will be executed.
The ng-change event is triggered at every change in the value. 
It will not wait until all changes are made, or when the input field loses 
focus.
The ng-change event is only triggered if there is a actual 
change in the input value, and not if the change was made from a JavaScript.
Syntax
    <element ng-change="expression"></element>
Supported by <input>, <select>, and <textarea>.
Parameter Values
| Value | Description | 
|---|---|
| expression | An expression to execute when an element's value changes. |