Challenges of modifying a scope object in Angular through reference

Question

Challenges of modifying a scope object in Angular through reference

I am encountering a challenge when trying to update a reference of an object within my code. Here's the scenario:

function modifyUserDetails(user) {
            $scope.initialUser = user;
            $scope.alteredUser = angular.copy(user);
        }

function ApplyUserChanges(form) {
            if (form.$valid) {
                $scope.initialUser = angular.copy($scope.alteredUser);
            }
        }

So far, everything is functioning as expected. I utilize modifyUserDetails(user) within an ng-repeat="user in users" loop to pass in the user object. When ApplyUserChanges is triggered, the initialUser object is successfully updated.

Initially, I assumed that since $scope.initialUser = user;, updating $scope.initialUser would also result in the user object within the users array getting updated, as I thought they shared the same reference. However, upon inspecting with ng-inspect, I noticed that although $scope.initialUser gets updated, the user within the users array remains unchanged.

Any insights on this behavior would be greatly appreciated.

javascript angularjs

Answer 1

Answer №1

You must make a change

// When you lose reference to the user object
$scope.originalUser = angular.copy($scope.editUser);

instead, use:

angular.extend($scope.originalUser, $scope.editUser)

Explanation of angular.copy:

var user = {name: 'John', age: 30},
        editUser, originalUser;
originalUser = user;
console.log(originalUser); // => {name: 'John', age: 30}
user === originalUser; // => true
editUser = angular.copy(user);
console.log(editUser); // => {name: 'John', age: 30}
user === editUser; => false
angular.extend(originalUser, editUser);
originalUser === user; // => true;
editUser === angular.copy(editUser); // => false
originalUser = angular.copy(editUser); // you have overwritten the reference to user with reference to new object angular.copy(editUser). Hence you have lost you reference to user.
originalUser === user; // => false;

Simplest form of angular.copy and angular.extend:

function copy(src) {
   var newObject = {};
   Object.keys(src).forEach(function(key) {
       newObject[key] = src[key];
   })
   return newObject;
}

function extend(dst, src) {
   Object.keys(src).forEach(function(key) {
       dst[key] = src[key];
   })
   return dst;
}

// Do not use these functions for real applications, only for explanation

Answer 2

You must make a change

// When you lose reference to the user object
$scope.originalUser = angular.copy($scope.editUser);

instead, use:

angular.extend($scope.originalUser, $scope.editUser)

Explanation of angular.copy:

var user = {name: 'John', age: 30},
        editUser, originalUser;
originalUser = user;
console.log(originalUser); // => {name: 'John', age: 30}
user === originalUser; // => true
editUser = angular.copy(user);
console.log(editUser); // => {name: 'John', age: 30}
user === editUser; => false
angular.extend(originalUser, editUser);
originalUser === user; // => true;
editUser === angular.copy(editUser); // => false
originalUser = angular.copy(editUser); // you have overwritten the reference to user with reference to new object angular.copy(editUser). Hence you have lost you reference to user.
originalUser === user; // => false;

Simplest form of angular.copy and angular.extend:

function copy(src) {
   var newObject = {};
   Object.keys(src).forEach(function(key) {
       newObject[key] = src[key];
   })
   return newObject;
}

function extend(dst, src) {
   Object.keys(src).forEach(function(key) {
       dst[key] = src[key];
   })
   return dst;
}

// Do not use these functions for real applications, only for explanation

Challenges of modifying a scope object in Angular through reference

Answer №1

Similar questions

The proxy encountered a TypeError when the trap for the property 'set' returned a falsish value

Access Vuex Getters in a separate JavaScript file

Investigate the CSS display property of an element using JavaScript

A guide to showcasing JSON data on a webpage using JavaScript

Retrieve the initial element from a JSON object to identify errors, without being dependent on its specific key name

Employing Angular.js $http.post in conjunction with Codeigniter WITH CSRF protection activated

Tips for creating a responsive layout to ensure that H2 achieves its optimal font size in a one-line DIV

Issues with displaying data in Angular ChartJS are troubling users

Error: Unable to access 'price' property of undefined - Next.js version 14.0.1

Trouble With Ajax Submission in CakePhp: Issue with Form Serialization

What is the best way to share in a LinkedIn group using JavaScript?

Fade out the jQuery message after a brief 2-second pause

Transform a complex PHP array into JSON format using JavaScript

Issue with D3: Events not triggering transitions

The function generalChannel.send does not exist

Tips for creating an expression within ng-if

Selecting the appropriate color code based on a specified value

Using the "$parent" variable within multi-level directives

What could be the reason for the GET request not functioning properly in Node.js?

ReactJS encounters errors even when the backend is returning a 200 OK status code