AngularJS: angular.identity with example

From AngularJS documentation

angular.identity: angular.identity(value);

A function that returns its first argument. This function is useful when writing code in the functional style.

function transformer(transformationFn, value) {

          return (transformationFn || angular.identity)(value); 

};

Example:

var app = angular.module('demoApp', []).controller(
    'DemoController',
    function($scope) {
     /*
     * lets have two demo functions
     */
     $scope.demoFunction1 = function(inputVal){
      console.log("First function called with parameter : "+inputVal);
     };
     
     $scope.demoFunction2 = function(inputVal){
      console.log("Second function called with parameter : "+inputVal);
     };     
     /*
     * To call above functions in functional way 
     */
     $scope.identityFunction = function(fn, val){
      return (fn||angular.identity)(val);
     }
     
     $scope.identityFunction($scope.demoFunction1, 19);
     $scope.identityFunction($scope.demoFunction2, 209);
    });

Plunker: https://plnkr.co/edit/h0hBCZih58Wuwu2ozm50?p=preview

Good Day :)