AngularJS is widely recognized as a highly popular JavaScript framework that encourages front-end developers to build dynamic web applications with simplicity. Having a solid understanding of typical interview questions and knowing how to answer them with accuracy will greatly boost an applicant’s chances of securing a position.
This blog presents Interview Questions In Angular JS that offer different topics including basic concepts, data binding, directives, services, controllers, and dependency injection. By concentrating on these core areas, candidates might show their deep knowledge and command of AngularJS during the interview process, impressing potential employers with their skills and expertise.
Understanding AngularJS
AngularJS is a widely used open-source framework that reduces web development by allowing the creation of engaging single-page applications (SPAs).
SPAs offer an effortless user interface by constantly updating content on the same page, instead of depending on conventional page loads for every click.
AngularJS has gained huge popularity due to its ability to utilize HTML as a template for developing cutting-edge web applications. With its ability to bridge the gap between HTML and application development frameworks, AngularJS provides a clear distinction for developers.
It offers essential data binding and code reuse features that empower your browsers to adapt to new syntax formats through directive specifics.
Key features and benefits of using AngularJS
1. MVC support
Many web development frameworks require programmers to divide the software code into three MVC components. Also, programmers must write additional code to connect these components.
AngularJS provides an easy feature that dynamically connects these separate pieces of code. It will decrease the amount of time of the developer.
2. Code reuse
Code reusability is a must for programmers. Angular JS enables them to take advantage of existing formats and make adjustments as needed. AngularJS utilizes HTML models, allowing the browser to easily parse them into the DOM (Document Object Model) using the powerful AngularJS compiler.
Mastering this technique can lead to substantial cost and time savings while enhancing the overall performance of your app.
3. Plug-and-play feature
AngularJS lets developers easily incorporate existing components into newly developed websites. You can simply copy the code directly to the component directory. In addition, the directory enables fast and efficient access to all framework assets.
4. Data binding feature
AngularJS can support both one-way and two-way data binding features. Developers can alter data in the model layer and update the view layer at the same time. With automatic data synchronization, the applications’ MVC layers can easily share and update data.
5. Support dependency injection (DI)
Dependency injection means introducing dependent functionality into software modules at runtime. AngularJS has an easy feature for Dependency Injection (DI). It allows code reusability, enabling developers to set up a specific service and utilize it in multiple modules.
Applications are developed, evaluated, and handled efficiently with the help of DI.
6. Real-time testing
AngularJS offers support for both end-to-end testing and unit testing. Testing features are essential to preserving high code quality and making sure the code remains free of bugs.
Moreover, testing is useful for code documentation and solving any dependencies that might exist.
7. Focus on UX
As time passes, the significance of user experience (UX) has grown heavily for businesses. It contributes an essential part in building trust and encouraging relationships with potential customers.
AngularJS empowers organizations to create Single Page Applications (SPAs) that offer users with simple access to every kind of data on a single page. It not only fulfills the demands of the business but also provides a superior user experience.
Top Interview Questions In Angular JS
Basic Interview Questions In Angular JS:
1. Explain the MVC architecture in AngularJS
Angular uses the Model-View-Controller (MVC) architectural pattern to properly structure the application’s components, enabling easy maintenance and expansion.
The MVC pattern breaks down the application into three separate parts: The Model: Encapsulates the data and business logic of the application.
The three parts are:
- Application data and business logic are in the Model. Data management and manipulation are its functions.
- The View renders the app’s UI. It shows data and allows user interaction.
- The Controller mediates between the Model and the View. It processes View user input, manipulates the Model, and updates the View with data changes.
2. What is data binding in AngularJS?
Data binding is the simple synchronization of data between the view and model components. AngularJS utilizes two-way data binding. With one-way binding, the scope variable in the HTML is set to the starting point assigned to its model.
3. What are directives in AngularJS?
Directives act as markers on DOM elements, enabling the manipulation of elements, attributes, CSS, and more. These can be utilized to generate personalized HTML tags that function as fresh, customized widgets.
AngularJS offers developers lots of built-in directives, such as ng-bind and ng-model, that greatly simplify common programming tasks.
4. What is scope in AngularJS?
Scopes act as an essential connection between the view and the controller in AngularJS. They are often referred to as the model components in the MVC architecture.
They are organized hierarchically to replicate the structure hierarchy of the DOM. AngularJS features a built-in $scope object that contains all the application data and linked methods.
5. Explain the concept of services in AngularJS
Services are independent objects that execute their functions. They interact via Dependency Injection, which allows the framework to organize and share code across the application.
AngularJS has integrated services. Developer-favored custom features are offered by AngularJS.
6. How does routing work in AngularJS?
Routing in AngularJS is handled by the ngRoute module or the more powerful ui-router module. Routing in AngularJS is an extremely successful feature that allows developers to quickly develop single-page applications (SPAs) with multiple views.
With AngularJS routing, you have a chance to quickly switch between different views without the need to reload the entire page.
7. What are filters in AngularJS?
Filters in AngularJS are used to format data offered to the user. Expressions can be enhanced by utilizing the pipe character (|). Here are some examples: currency, date, filter, JSON, and lowercase.
Advance Interview Questions In Angular JS:
8. What is a $digest cycle in AngularJS?
Knowing the $digest cycle is essential in AngularJS as it ensures that any changes in the model are quickly reflected in the view. It is automatically triggered, yet you can also manually invoke it using $scope.$digest().
9. How to optimize the performance of an AngularJS application?
To optimize performance in AngularJS applications:
Use one-time binding (::) for static content.
Limit the use of watchers.
Use ng-if instead of ng-show/ng-hide when possible.
Minimize DOM manipulations.
Use $scope.$applyAsync() to batch updates.
10. How to handle errors in AngularJS?
Error handling in AngularJS can be managed using:
$log service for logging errors.
Custom error handling services.
Promises’ catch method to handle errors in asynchronous operations.
11. Write a syntax to send sample HTTP POST request in AngualrJS?
$http({
method: “POST”,
url: “URL”,
data: JSON.stringify(value),
contentType: ‘application/json’
}).then(function (successResponse)
{
// success callback action of the request
},function (errorResponse)
{
// error callback action of the request
});
12. Is it possible to create nested controllers?
<div ng-controller=”mainController”>
<p>{{message}} {{name}}!</p>
<div ng-controller=”childController1″>
<p>Welcome to our app, {{name}}!</p>
<div ng-controller=”subChildController2″>
<p>{{message}} {{name}}! You are our esteemed guest {{name}}.</p>
</div>
</div>
</div>
13. What are the different phases of the lifecycle of AngularJS Scope?
- Creation: $injector creates rootScope during application bootstrap. New directive-related child scopes are established during template linking.
- Registration of viewers: Here, directives register scope object watches to transmit model values to DOM.
- Model mutation: The scope must include model mutations.$apply() to appropriately observe them. AngularJS implicitly does this for synchronous and asynchronous work requests.
- Mutation observation: After $apply, the digest cycle observes scope model mutations. The $watch listener is invoked on the model if the $watches expressions detect model mutations.
- Scope destruction: When child scopes are superfluous, the creator must destroy them using scope.$destroy(). This stops $digest cycle propagations and frees child scope memory.
14. How will you hide an HTML tag element on click of a button click in AngularJS? Write a program for the same.
<!DOCTYPE html>
<html>
<head>
<meta chrset=”UTF 8″>
<title>Button Click Hide</title>
</head>
<body>
<script src=”https://code.angularjs.org/1.6.9/angular.js”></script>
<script src=”https://code.jquery.com/jquery-3.3.1.min.js”></script>
<div ng-app=”buttonDemo” ng-controller=”buttonDemoController”>
<button ng-click=”hideTag()”>Hide IntervieBit</button>
<div ng-hide=”hideFlag”>InterviewBit</div>
</div>
<script type=”text/javascript”>
var app = angular.module(‘buttonDemo’,[]);
app.controller(‘buttonDemoController’,function($scope){
$scope.hideFlag = false;
$scope.hideTag = function(){
$scope.hideFlag = true;
}
});
</script>
</body>
</html>
15. What are the lifecycle hooks available?
- The ngOnInit() method is a callback function that is triggered when the change detector detects any changes in the scope model for the first time before any view has been checked. This function is called only once when the directive is created.
- The ngOnChanges() callback function is triggered whenever changes are detected in the scope model. It allows us to define the necessary actions to be taken when a property is changed. This method is invoked before ngOnInit() during the instantiation of the directive and is triggered whenever there are changes in the scope model.
- The ngDoCheck() callback method performs change-detection tasks and is called only after the default change-detector has been executed.
- The ngAfterContentInit() method is called only once, immediately after AngularJS finishes initializing all the content of the directives.
- This callback method is called after the default change-detector finishes checking the content of the directives.
- The ngOnDestroy() method is utilized to perform necessary clean-up tasks before the directives or properties of a component are destroyed. They are valuable for preventing memory leaks and unsubscribing from any unnecessary observables.
- The ngAfterViewChecked() method is called as soon as the default change-detector finishes one cycle of change-check.
16. How would you implement a custom filter in AngularJS?
To implement a custom filter, use the filter method on your module:
angular.module(‘myApp’).filter(‘customFilter’, function() {
return function(input) {
// Filter logic here
return output;
};
});
17. How would you manage state in a large AngularJS application?
State management can be effectively handled through the use of services to facilitate data sharing between controllers. Also, for more complex state management requirements, one can leverage third-party libraries such as ng-redux or angular-local-storage.
18. What approach would you take to migrate an existing project to AngularJS?
Outline a detailed migration plan:
- Assess the existing project structure and dependencies.
- Incrementally integrate AngularJS components.
- Ensure thorough testing at each step.
- Refactor and optimize code as needed.
19. How do you implement authentication in Angular?
Authentication can be implemented using JWT tokens, Angular guards, and interceptors to manage login and secure routes.
import { Injectable } from ‘@angular/core’;
@Injectable({
providedIn: ‘root’
})
export class AuthService {
constructor() { }
isLoggedIn(): boolean {
// Implement your authentication logic here
// For example, check if the user token exists in localStorage
return !!localStorage.getItem(‘userToken’);
}
// Add other auth-related methods like login, logout, etc.
}
20. Explain the purpose of Angular Elements.
- Web Component Integration: Enables Angular components to be bundled as custom elements (web components) that are compatible with any HTML page or framework.
- Reusability: Facilitates the reuse of Angular components across various projects and frameworks, promoting code sharing and maintaining consistency.
- Interoperability: Facilitates the seamless integration of Angular components into applications built with different frameworks, ensuring greater flexibility and compatibility.
- Encapsulation is a key feature of Angular JS. It allows for the creation of self-contained components that encapsulate their logic, styles, and templates. This helps to minimize conflicts and maintain a clean structure in larger applications.
21. What are the different types of filters in Angular?
Below are the various filters supported by Angular:
- currency: Format a number to a currency format.
- date: Format a date to a specified format.
- filter: Select a subset of items from an array.
- json: Format an object to a JSON string.
- limit: To Limits an array/string, into a specified number of elements/characters.
- lowercase: Format a string to lower case.
- number: Format a number to a string.
- orderBy: Orders an array by an expression.
- uppercase: Format a string to upper case.
22. What are events in Angular?
- ng-click
- ng-copy
- ng-cut
- ng-dblclick
- ng-keydown
- ng-keypress
- ng-keyup
- ng-mousedown
- ng-mouseenter
- ng-mouseleave
- ng-mousemove
- ng-mouseover
- ng-mouseup
- ng-blur
23. What is the difference between ng-model and ng-bind?
ng-model binds the value of HTML controls (input, select, textarea) to application data, enabling two-way data binding. ng-bind only binds data to HTML elements for one-way binding.
24. How can you create a custom directive in AngularJS?
Custom directives can be created using the directive function on a module. They require a name, a linking function, and options to define their behavior.
25. What is an AngularJS module? How do you define one?
An AngularJS module defines an application. It is a container for different parts of an app, such as controllers, services, filters, directives, etc. Modules can be defined using angular.module.
25. What is an AngularJS module? How do you define one?
An AngularJS module defines an application. It is a container for different parts of an app, such as controllers, services, filters, directives, etc. Modules can be defined using angular.module.
26. How do you create a service using the factory method in AngularJS?
A service can be created using the factory method, which returns an object or a function.
27. What are providers in AngularJS?
Providers are the most configurable way to create a service. They provide a provider method that returns a $get function, which then returns the service instance.
27. What are providers in AngularJS?
Providers are the most configurable way to create a service. They provide a provider method that returns a $get function, which then returns the service instance.
28. Explain the concept of transclusion in AngularJS.
Transclusion is the process of including a portion of the DOM tree from one part of the document into another. It is often used in directives to keep the original content.
29. What are $q and $promise in AngularJS?
‘$q’ is a service that helps you run functions asynchronously, and $promise is an object representing the eventual completion (or failure) of an asynchronous operation and its resulting value.
30. How do you test an AngularJS application?
AngularJS applications can be tested using tools like Jasmine for unit testing and Protractor for end-to-end testing. Tests can be written to check controllers, services, directives, filters, and other components.
31. What is the $http service in AngularJS?
The $http service is a core AngularJS service that facilitates communication with remote HTTP servers via the browser’s XMLHttpRequest object or via JSONP.
32. What is the purpose of $location service in AngularJS?
The $location service parses the URL in the address bar and makes changes to the URL.
33. What is the difference between $watch, $digest, and $apply in AngularJS?
$watch registers a listener callback to be executed whenever the watched expression changes. $digest iterates through all the watchers and checks if they need to be updated. $apply is used to execute an expression and trigger the $digest cycle.
34. What is $rootScope in AngularJS?
$rootScope is the top-level scope that is available throughout the AngularJS application. All other scopes are child scopes of $rootScope.
35. What are Angular interceptors?
Interceptors are part of the HTTP client module that allow inspection and transformation of HTTP requests and responses.
36. Explain the purpose of NgZone in Angular.
In Angular, NgZone is a service that helps manage the execution of asynchronous operations outside of Angular’s change detection mechanism. Its primary purpose is to handle the integration of non-Angular code and events into the Angular application’s zone, which is essential for ensuring proper change detection and UI updates.
37. How can you reset a $timeout and disable a $watch()?
In AngularJS (Angular 1.x), $timeout and $watch are services provided by Angular’s core that allow you to perform asynchronous operations and monitor changes to scope variables, respectively.
Conclusion
Being well-prepared for AngularJS Interview questions requires an excellent understanding of fundamental and advanced concepts.
By being knowledgeable about typical interview questions and improving your abilities, you’ll be fully prepared to handle any interview with self-assurance. Continuously keep in mind that success comes from dedication to going on learning and plenty of practical experience.
FAQs
1. What is AngularJS and how does it differ from other JavaScript frameworks?
Google maintains the open-source front-end web application framework AngularJS. Unlike other frameworks, it uses two-way data binding to synchronize the model and display data automatically.
2. Can you explain the concept of directives in AngularJS?
AngularJS directives tell the HTML compiler to apply a behavior to a DOM element. Create custom HTML tags, attributes, classes, and comments with them.
3. How does dependency injection work in AngularJS?
The AngularJS dependency injection design pattern loosely couples components. It includes giving component dependencies like services or objects rather than having it generate or find them.
4. What are the benefits of using services in AngularJS?
AngularJS services are reusable components with specialized functionality. They improve code reuse, testability, and application concern separation.
5. How does routing work in AngularJS?
By mapping URLs to views and controllers, AngularJS routes enable single-page apps. This lets users switch between app components without reloading the page.
