AngularJS is a JavaScript framework by Google, that streamlines dynamic single-page web app creation. This article presents a comprehensive compilation of AngularJS Interview Questions and Answers, offering deep insights into its concepts. Explore key topics, tackle complex queries, and enhance your AngularJS proficiency for successful interviews.
AngularJS Interview Questions and Answers
1. What is AngularJS and who created it?
AngularJS, an open-source JavaScript front-end framework, excels in building single-page web applications (SPAs). With features like dynamic binding and dependency injection, it transforms static HTML into dynamic content. Developed in 2008-2009 by Misko Hevery and Adam Abrons, AngularJS is maintained by Google and boasts continuous growth and evolution, with the latest stable version being 1.7.7. It extends HTML attributes with directives and facilitates seamless data binding. It’s essential to distinguish between AngularJS and Angular, as they are distinct frameworks.
2. What are the features of AngularJS?
The main features of AngularJS are listed below:
- Testable: AngularJS applications are easily testable, enabling efficient testing of various components and functionalities.
- Data Binding: Facilitates synchronization of data between model and view components.
- Controller: JavaScript functions bound to scope, aiding in application logic implementation.
- Services: In-built services like $http for making XMLHttpRequests and AJAX calls.
- Scope: Special objects connecting models and acting as glue between view and controller.
- Filters: Support for in-built and custom filters for array subsetting and data filtering.
- Directives: Markers of DOM elements, creating custom HTML tags and widgets.
- Routing: Switching views based on conditions for dynamic application navigation.
- MVC Pattern: Model manages data, views display it, and controllers handle application logic.
- Dependency Injection: Simplifies application development, maintenance, and testing by resolving component dependencies.
3. What is scope and Data Binding in AngularJS?
- Scope: Scope in AngularJS is the binding part of HTML view and JavaScript controller. When you add properties into the scope object in the JavaScript controller, only then the HTML view gets access to those properties. There are two types of Scope in AngularJS.
- Data Binding: Angular provides a function Data Binding which helps us to have an almost real-time reflection of the input given by the user i.e. it creates a connection between Model and View.
4. How many types of data bindings are there in AngularJs?
There are four kinds of data bindings in AngularJS, these are:
- Event Binding
- Property Binding
- Two way Binding
- Interpolation Binding
5. Differences between one-way binding and two-way binding
- Property Binding: Similar to Java, variables defined in the parent class can be inherited by child class that is templates in this case. The only difference between Interpolation and Property binding is that we should not store non-string values in variables while using interpolation. So if we have to store Boolean or other data types than use Property Binding.
- Interpolation Binding: Angular interpolation is used display a component property in the respective view template with double curly braces syntax. Interpolation is used to transfer properties mentioned in component class to be reflected in its template.
6. Explain the Services and Expression in AngularJS
- Services: Services are used to create variables/data that can be shared and can be used outside the component in which it is defined.
- Expression: Expressions in AngularJS are used to bind application data to HTML. The expressions are resolved by Angular and the result is returned back to where the expression is written.
7. What is the key difference between angular expressions and JavaScript expressions?
AngularJS expression can be written in HTML but JavaScript expression can’t and Filters are supported by AngularJS but not by JavaScript. We cannot use conditional iterations, loops, and exceptions in AngularJs, but we can use all of these conditional properties in JavaScript expressions.
8. Write all steps to configure an Angular App(ng-app)?
- Step 1: The angular.module will be created at first.
- Step 2: A controller will be assigned to the module.
- Step 3: The module will be linked with the HTML template with an angular app(ng-app).
- Step 4: The HTML template will be linked with the controller with an ng-controller directive.
9. With options on page load how you can initialize a select box?
You can initialize a select box using ng-init directive when options on page load.
<div ng-controller = " apps/dashboard/account " ng-switch
On = "! ! accounts" ng-init = " loadData ( ) ">10. What are Directives in AngularJS and name few of them?
Directives in AngularJS are markers on DOM elements that tell Angular’s HTML compiler to attach a specified behavior to that DOM element. Some directives include ng-model, ng-repeat, ng-if, ng-show, ng-hide, ng-click, and ng-class.
11. What are the advantages of using AngularJS?
There are several advantages to AngularJS. Supports the MVC pattern support two ways of data binding using AngularJS. It has per-defined form validations Supported both client-server communication and animations.
12. What AngularJS routing does?
Routing in AngularJS is used when the user wants to navigate to different pages in an application but still wants it to be a single page application. AngularJS routes enable the user to create different URLs for different content in an application. The ngRoute module helps in accessing different pages of an application without reloading the entire application.
13. How to share data between controllers in AngularJS?
We have to create a service first. The Services are used to share data between controllers in AngularJS. We use events, $parent, next sibling, and controller by using a $rootScope.
14. What are the steps for the compilation process of HTML?
- Step 1: Using the standard browser API, first, the HTML is parsed into DOM
- Step 2: By using the call to the $compile() method, a compilation of the DOM is performed. The method traverses the DOM and then matches the directives.
- Step 3: Link the template with a scope by calling the linking function returned from the previous step.
15. What is string interpolation in AngularJS?
In AngularJS, during the compilation process, it matches the text and attributes using interpolate service to see if they contain embedded expressions. As part of the normal digest cycle, these expressions are updated and registered as watches.
16. How many types of Directives are available in AngularJS?
There are four kinds of directives in AngularJS those are described below:
- Element directives
- Attribute directives
- CSS class directives
- Comment directives
17. What is injector?
The injector in AngularJS is basically a service locator. It is used to invoked methods and for loading modules. There can be only one injector in a single AngularJS app.
18. What is factory method in AngularJS?
AngularJS Factory Method makes the development process of AngularJS application more robust. A factory is a simple function that allows us to add some logic to a created object and return the created object. The factory is also used to create/return a function in the form of reusable code which can be used anywhere within the application. Whenever we create an object using a factory it always returns a new instance for that object. The object returned by the factory can be integrated(injectible) with different components of the Angularjs framework such as controller, service, filter or directive.
19. What is the digest cycle in AngularJS?
It is the most important part of the process of data binding in AngularJS. It basically compares the old and new versions of the scope model. The digest cycle triggered automatically. If we want to trigger the digest cycle manually then we can use $apply().
20. What is the difference between Angular and AngularJS?
| Aspect | Angular | AngularJS |
|---|---|---|
| Version | Angular is version 2.0 and later, including Angular 12. | AngularJS is version 1.0, developed by Google. |
| Language | Written in TypeScript, a superset of JavaScript. | Written in JavaScript. |
| Architecture | Follows component-based architecture. | Follows MVC (Model-View-Controller) architecture. |
| Performance | Offers better performance and enhanced features. | Performance is comparatively lower due to digest cycle. |
| Mobile Support | Provides better support for mobile development. | Lacks robust support for mobile development. |
|
Data Binding |
Two-way data binding |
One-way data binding |
|
Dependency Injection |
Uses hierarchical injectors |
Uses global scope for dependency injection |
Conclusion
This article covers frequently asked AngularJS interview questions for both fresher and experienced developers. AngularJS introduced dependency injection and simplified single-page app development, leading to widespread adoption in various companies for its benefits, ease of use, and extensibility.