🚀 AngularJS Interview Questions: Detailed Explanation with Code Examples
Are you preparing for AngularJS interviews in 2025? This comprehensive guide brings you the most important AngularJS interview questions with detailed explanations and practical code examples to strengthen your concepts. Whether you’re a fresher or an experienced developer, mastering these questions will give you confidence for your next frontend role.
Explore the top topics, practice real coding examples, and enhance your AngularJS skills effectively.
👉 For additional interview preparation, check out this Top Interview Questions.
1. What is AngularJS?
Answer: AngularJS is a JavaScript-based open-source front-end framework maintained by Google for developing single-page applications (SPAs) with MVC architecture.
Example Use:
Creating dynamic forms, real-time dashboards, and data-binding UIs.
2. What are the key features of AngularJS?
Answer:
- Two-way data binding
- MVC architecture
- Directives
- Dependency injection
- Templates
3. Explain two-way data binding in AngularJS.
Answer: Two-way data binding automatically synchronizes data between model and view.
Example:
<div ng-app=”myApp” ng-controller=”myCtrl”>
<input ng-model=”name”>
<p>Hello {{name}}</p>
</div>
<script>
angular.module(‘myApp’, [])
.controller(‘myCtrl’, function($scope) {
$scope.name = “AngularJS”;
});
</script>
Typing in the input updates {{name}} dynamically.
4. What is a directive in AngularJS?
Answer: A directive is a special marker on DOM elements (attribute, element, comment, or class) that tells AngularJS to attach specific behaviour.
Example: ng-model, ng-repeat, ng-if
5. What is the role of $scope in AngularJS?
Answer: $scope is an object that binds the controller and view, holding model data.
Example:
$scope.name = “Angular”;
Accessible in view as {{name}}.
6. Explain controllers in AngularJS.
Answer: Controllers are JavaScript functions that control the data and behaviour of HTML views.
Example:
app.controller(“myCtrl”, function($scope) {
$scope.message = “Hello AngularJS”;
});
7. What is an AngularJS module?
Answer: A module defines an application in AngularJS using:
var app = angular.module(‘myApp’, []);
It groups controllers, services, directives, etc.
8. What are filters in AngularJS?
Answer: Filters format data displayed to the user.
Example:
<p>{{ price | currency }}</p>
Converts 50 to $50.00.
9. Explain services in AngularJS.
Answer: Services are singleton objects used to share data and logic across controllers.
Example:
app.service(‘myService’, function() {
this.sayHello = function() {
return “Hello!”;
};
});
10. What is dependency injection in AngularJS?
Answer: Dependency Injection (DI) in AngularJS is a design pattern where components (controllers, services, filters, directives) are given their dependencies instead of creating them manually. AngularJS injects these dependencies automatically when the component is instantiated.
Detailed Explanation:
- DI promotes loose coupling and easier unit testing.
- Dependencies (services or objects required by a component) are defined as parameters, and AngularJS resolves and provides them.
var app = angular.module(‘myApp’, []);
app.controller(‘myCtrl’, function($scope, $http) {
$scope.message = “Dependency Injection Example”;
$http.get(“/api/data”)
.then(function(response) {
$scope.data = response.data;
});
});
11. What is $http service in AngularJS?
Answer: $http is used to make AJAX calls to communicate with backend APIs.
Example:
$http.get(“/api/data”)
.then(function(response) {
$scope.data = response.data;
});
12. What is $watch in AngularJS?
Answer: $watch is used to observe changes in a scope variable and react accordingly.
13. Difference between ng-if and ng-show/ng-hide.
ng-if | ng-show/ng-hide |
Adds/removes element from DOM | Changes CSS display property |
Better for conditional DOM rendering | Better for toggle visibility |
14. What is $digest cycle?
Answer: The $digest cycle is the process by which AngularJS checks for changes in the scope model values and updates the view accordingly. It is an internal loop that watches for changes in variables and keeps the model and view in sync.
Detailed Explanation:
- AngularJS uses two-way data binding. To maintain this, it checks all watchers (variables watched for changes) during the $digest cycle.
- If a value changes, the watcher updates the DOM wherever it is used.
15. What are custom directives?
Answer: Custom directives in AngularJS are user-defined directives that allow developers to create reusable components or extend HTML functionality with custom behaviour.
Detailed Explanation:
- AngularJS comes with built-in directives like ng-model, ng-repeat, ng-if, etc.
- Using custom directives, developers can:
- Create custom HTML tags or attributes.
- Encapsulate reusable UI components and behaviour.
- Enhance code modularity and maintainability.
- Create custom HTML tags or attributes.
Example:
app.directive(‘myDirective’, function() {
return {
template: ‘<h1>This is a custom directive</h1>’
};
});
16. Explain routing in AngularJS.
Answer: Routing in AngularJS is the mechanism that allows you to create Single Page Applications (SPAs) by navigating between different views (templates) without reloading the entire page. It uses the ngRoute module to configure routes and map URLs to views and controllers.
Detailed Explanation:
✔️ Routing helps in:
- Loading different templates based on the URL.
- Binding each template to a specific controller.
- Creating a seamless SPA experience by avoiding full page reloads.
17. Example of AngularJS routing.
var app = angular.module(“myApp”, [“ngRoute”]);
app.config(function($routeProvider) {
$routeProvider
.when(“/home”, { templateUrl : “home.html” })
.when(“/about”, { templateUrl : “about.html” });
});
18. What is $routeProvider?
Answer: $routeProvider is a service provided by the ngRoute module in AngularJS used to configure routing in Single Page Applications (SPAs). It defines how your app responds to different URL paths by mapping them to specific templates and controllers.
Detailed Explanation:
- $routeProvider allows you to set up routes using .when() and .otherwise() methods.
- It determines which view (template) to display and which controller to use when a particular URL is accessed.
- It helps create navigation within a SPA without reloading the entire page.
19. Difference between factory and service.
Factory | Service |
Returns the value/object explicitly | Uses this to attach properties and methods |
More flexible | Simpler syntax |
20. What is $rootScope?
Answer: $rootScope is a global scope object in AngularJS that is created when your application is initialized. It acts as the parent scope of all other $scope objects in your application.
Detailed Explanation:
- Every AngularJS application has a single $rootScope, created automatically.
- All controllers and scopes inherit from $rootScope.
- Variables and functions defined on $rootScope are accessible in all controllers, directives, and views throughout the app unless shadowed by local $scope.
21. What are single page applications (SPA)?
Answer: A Single Page Application (SPA) is a web application or website that loads a single HTML page and dynamically updates content as the user interacts with the app, without reloading the entire page from the server.
Detailed Explanation:
- In traditional multi-page applications (MPA), each user action requests a new page from the server.
- In SPAs, after the initial page load:
- Only data is exchanged with the server, not full pages.
- JavaScript dynamically updates the content in the browser.
- The URL changes are handled on the client side (using routing), maintaining browser history without reloading pages.
- Only data is exchanged with the server, not full pages.
Advantages of SPAs:
- Faster user experience after initial load.
- Reduced server load as only data is exchanged.
- Smooth navigation and app-like interactions.
- Can work offline with service workers (PWA concept).
22. What is the use of $apply?
Answer: $apply() is an AngularJS scope method used to execute expressions or functions outside AngularJS’s context and trigger a $digest cycle, ensuring that any changes to scope variables are detected and the view is updated accordingly.
Detailed Explanation:
- AngularJS automatically runs the $digest cycle when changes happen within its ecosystem (e.g. directives, ng-click, $http, $timeout).
- However, if changes are made outside AngularJS (e.g. inside setTimeout, external JS libraries, or jQuery callbacks), Angular does not detect these changes automatically.
23. What is $compile?
Answer: $compile is a service in AngularJS that compiles HTML strings or DOM elements into a template function, which links the template with a scope to produce a live view.
Detailed Explanation:
- AngularJS uses $compile internally to process directives and expressions in the HTML, creating a link function that binds the compiled template to a scope.
- This process enables dynamic addition of HTML content containing AngularJS bindings or directives.
24. Explain $location service.
Answer: The $location service in AngularJS is used to interact with and manipulate the browser’s URL in a single-page application (SPA) without reloading the page. It is part of AngularJS’s routing mechanism.
Detailed Explanation:
- $location provides methods to read or change the URL in the address bar.
- It works with the HTML5 History API (if enabled) or hashbang URLs.
- It allows you to get different parts of the URL such as path, search (query parameters), hash, protocol, host, and port.
25. How to handle exceptions in AngularJS?
Answer: In AngularJS, exception handling is done using built-in services and best practices to catch errors gracefully and handle them without crashing the application. AngularJS provides $exceptionHandler for global error handling.
Detailed Explanation:
- Using try-catch blocks:
For synchronous code, you can use regular JavaScript try-catch to handle exceptions locally.
try {
// code that may throw an error
var result = riskyOperation();
} catch (e) {
console.error(“Error occurred:”, e);
}
2. Using $exceptionHandler Service:
- AngularJS provides a global error handler service called $exceptionHandler.
- By default, it logs errors to the console, but you can override it to implement custom handling, such as logging errors to a server.
26. What are expressions in AngularJS?
Answer: Similar to JavaScript expressions but evaluated against the scope.
Example: {{ 5 + 5 }} displays 10.
27. What is interpolation?
Answer: Interpolation in AngularJS is the process of binding expressions into the HTML to display dynamic data. It is done using double curly braces {{ expression }}, which AngularJS evaluates and replaces with the actual value in the view.
Detailed Explanation:
- Interpolation evaluates AngularJS expressions in the context of the current scope.
- It allows dynamic rendering of data from the controller or scope into the HTML view.
- It can include variables, operations, and function calls.
28. How to make an HTTP POST request using $http?
Example:
$http.post(“/api/add”, { name: “Angular” })
.then(function(response) {
$scope.message = response.data;
});
29. Explain $timeout service.
Answer: The $timeout service in AngularJS is similar to JavaScript’s setTimeout function. It executes a function after a specified delay, but with an important difference: it is integrated with AngularJS’s digest cycle, ensuring changes are updated in the view automatically.
Detailed Explanation:
- $timeout is a wrapper around window.setTimeout.
- It returns a promise that gets resolved when the delay completes.
- Automatically triggers a digest cycle after execution, so scope changes are detected and the view is updated without manually calling $apply().
30. What are templates in AngularJS?
Answer: Templates are HTML with AngularJS-specific elements and attributes, rendered with data and directives to form views.
Detailed Explanation:
- Templates contain HTML code plus AngularJS directives, expressions, filters, and bindings.
- They are combined with a controller and model data to produce dynamic views.
- Templates can be:
- Inline templates: defined within the HTML file itself.
- External templates: loaded from separate HTML files using routing.
- Inline templates: defined within the HTML file itself.
These AngularJS interview questions with detailed explanations and code examples will boost your preparation for upcoming interviews. By understanding the concepts deeply and practising practical implementations, you can confidently tackle any AngularJS question.
🔗 For further reading, explore the Top 100 Javascript Interview Questions to strengthen your JavaScript fundamentals alongside AngularJS concepts.
Keep revising, keep practising, and ace your AngularJS interviews!
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