How to check the existence of key in an object using AngularJS ?

Last Updated : 04 Aug, 2022

Given an object containing a (key, value) pair and the task is to check whether a key exists in an object or not using AngularJS. In order to check the existence of a key in an object, we will create an object having properties in the form of a key: value pair. Define a temporary variable that will hold the initial key of an object. Create a function expression that will be utilized to check whether the temporary variable that holds an initial key, exists or not in the given object, by comparing them.

Approach: The approach is to use the in operator to check whether a key exists in an object or not. In the first example, the key "Prop_1" is input and it exists in the object. In the second example, the user can check which key they want to check for existence.

Example 1: In this example, the key "Prop_1" is input and checking whether it exists in the object or not.

HTML

<!DOCTYPE HTML>
<html>

<head>
    <script src=
"//ajax.googleapis.com/ajax/libs/angularjs/1.2.13/angular.min.js">
    </script>
    <script>
        var myApp = angular.module("app", []);
        myApp.controller("controller", function($scope) {
            $scope.obj1 = {
                "Prop_1": 1,
                "Prop_2": 2,
                "Prop_3": 3
            };
            $scope.textval = "Prop_1";
            $scope.checkK = function() {
                var txtVal = $scope.textval;
                if(!(txtVal in $scope.obj1)) {
                    $scope.res = "Key not Exists.";
                } else {
                    $scope.res = "Key Exists";
                }
            }
        });
    </script>
</head>

<body style="text-align:center;">
    <h1 style="color:green;">
        GeeksforGeeks
    </h1>
    <h3>
        Check if a key exists in
        an object in AngularJS
    </h3>
    <div ng-app="app">
        <div ng-controller="controller"> Object - {{obj1}}
            <br><br>
            Enter the key:
            <input type="text" ng-model="textval">
            <br><br>
            <button ng-click="checkK()">
                 Check here
            </button>
            <br><br> {{res}}
        </div>
    </div>
</body>
</html>

Output:

Example 2: In this example, the user will check which key they want to check for existence in the given object.