AngularJS | ng-change Directive

Last Updated : 26 Mar, 2019

The ng-change Directive in AngularJS is used whenever the value of an input element changes. The expression is evaluated immediately whenever there is a change in the input value. It requires a ng-model directive to be present. It is triggered whenever there is any single change in the input. It can be used with input elements like <input>, <textarea>, <checkbox> and <select>

Syntax:

<element ng-change="expression"> Contents... </element>

Where expression refers to the expression to execute whenever the value of input changes.

Example 1: This example uses ng-change Directive to display/hide some content using checkbox.

<!DOCTYPE html> 
<html> 
      
<head> 
    <title>ng-change Directive</title> 
  
    <script src= 
"https://ajax.googleapis.com/ajax/libs/angularjs/1.6.9/angular.min.js"> 
    </script> 
  
    <script type="text/javascript"> 
        var app = angular.module('geek', []); 
        app.controller('app', function ($scope) { 
            $scope.show = function () { 
                if ($scope.check == true) 
                    $scope.result = true; 
                else 
                    $scope.result = false; 
            } 
        }); 
    </script> 
</head> 
  
<body style="padding: 30px"> 
    <div ng-app="geek" ng-controller="app"> 
        <h1 style="color:green">GeeksforGeeks</h1> 
        <h2>ng-change Directive</h2> 
          
        Check to show/hide details <input type="checkbox"
                    ng-change="show()" ng-model="check"> 
        <br><br> 
          
        <div style="padding:10px; border:1px solid black;  
                width:30%;color:green" ng-show='result'> 
            GeeksforGeeks is the computer science 
            portal for geeks. 
        </div> 
    </div> 
</body> 
  
</html> 

Output:
Before checked the checkbox:
ng-change
After checked the checkbox:

Example 2: This example returns the number of times state of checkbox is changed and also the current state of checkbox.

<!DOCTYPE html> 
<html> 
      
<head> 
    <title>ng-change Directive</title> 
  
    <script src= 
"https://ajax.googleapis.com/ajax/libs/angularjs/1.6.9/angular.min.js"> 
    </script> 
</head> 
  
<body ng-app="geek" style="text-align:center"> 
    <h1 style="color:green">GeeksforGeeks</h1> 
    <h2>ng-change Directive</h2> 
    <div ng-controller="prop"> 
        <div> 
            Are you a developer:   
            <input type="checkbox" ng-model="isTrue"
            ng-change="cnt=cnt+1" ng-init="cnt=0"/> 
        </div> 
        Count: {{cnt}} 
        <pre>{{isTrue}}</pre> 
    </div> 
      
    <script> 
        var app = angular.module("geek", []); 
        app.controller('prop', ['$scope', function ($app) { 
            $app.isTrue = false; 
        }]); 
    </script> 
</body> 
  
</html> 

Output:
Before checked the checkbox:
ng-change
After checked the checkbox:

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