Angular Interview questions & answers

Angular JS Interview has been  rated as the top programming language for web developers since 2019. Therefore, this is the right time to become an Angular developer: lots of companies are looking for skilled programmers in this language.

If you are going to apply for those positions, you must be prepared to answer some angular questions during the job interview, as well as be successful in coding tests. But while keeping up your programming practice, here we have compiled for you some of the most common angular interview questions and answers that you should expect in your interview this year.

Common Angular Interview questions

At the beginning of the interview, you will be asked some general questions about Angular concepts.

What is Angular?

It is a TypeScript-based open-source web application framework. It hasbeen developed and maintained by Google as an easy and powerful language to build front end web-based applications. This language integrates features like dependency injection, declarative templates, end-to-end tooling and others that make web application development easier.

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Mention some Angular features

To be an ideal front end JavaScript framework, Angular is capable of:

  • Create accessibility applications: it uses ARIA-enabled components, built-in a11y test infrastructure, and developer guides.
  • Provides support for command-line interface tools: Those can be used to add components, instant deploying, testing, etc.
  • Gives Animation Support: its intuitive API lets you create high-performance, complex animation timelines with little code.
  • Be used for Cross-Platform App Development: Angular lets you build efficient and powerful desktop, native, and progressive web apps. It provides support for Ionic, Cordova, or NativeScript, using modern web platform capabilities. It can also be used for building desktop apps for Windows, Linux or macOS.
  • Code Generation: is able to convert templates into highly-optimized code, to be used in modern JavaScript virtual machines.
  • Code Splitting: thanks to its Component Router, Angular has automatic code-splitting, so apps load faster.
  • Make synergy with Popular Code Editors and IDEs: Angular adds code completion, instant errors and more with code editors and IDEs.
  • Make Templates: it create UI views with template syntax.
  • Testing: By using Karma, Angular allows frequent unit tests, and Protractor allows running stable scenario tests.

What are the advantages and disadvantages of using Angular?

Among the advantages of using Angular are:

  • Support for dependency injection, validations and RESTful services
  • Support for two-way data-binding
  • It supports static and Angular templates
  • It uses the MVC pattern architecture
  • Strong features such as Animation and Event Handlers
  • Good client and server communication
  • Great community support
  • Ability to add custom directives

On the other hand, the disadvantages of using Angular are:

  • Angular requires effort and time the be learned
  • Dynamic applications sometimes perform badly
  • Complex SPAs are inconvenient and laggy.

Remark some features of Angular 7

The major difference between Angular 7 andprevious versions is that this version comes with splitting in @angular/core to reduce size. Since not every module is required, in Angular 7 each split will have no more than 418 modules.

Other differences are the drag-and-drop and virtual scrolling, as well as unloading elements from the DOM. Also, Angular 7 comes with a new version of the ng-compiler.

What are the difference between Angular and AngularJS?

  • In Architecture: AngularJS supports the MVC design model. Angular relies on components and directives.
  • In Dependency Injection: Angular supports a hierarchical Dependency Injection with tree-based change detection. AngularJS doesn’t support Dependency Injection.
  • In Expression Syntax: In AngularJS, a specific ng directive is required while Angular use () and [] for blinding an event and accomplishing property binding.
  • In Mobile Support: AngularJS doesn’t have mobile.
  • In Recommended Language: AngularJS relies on JavaScript. Angular is based on TypeScript.
  • In Routing: AngularJS uses $routeprovider.when(). Meanwhile, Angular uses @RouteConfig{(…)}
  • In performance: Two-way data binding in AngularJS reduces effort and time, but Angular is faster due to upgraded features.
  • In Structure: Angular provides easier development and maintenance of large applications.
  • In Support: There’s no official support or updates for AngularJS. On the contrary, Angular has active support with updates.

What is the difference between Angular and backbone.js?

There are several main differences:

  • In type: Angular is an open-source JS-based front-end web application framework. Backbone.js is a lightweight JavaScript library featuring a RESTful JSON interface and MVP framework.
  • In the Approach to Testing: In Angular, unit testing is preferred and the testing process is smoother. Backbone.js allows a swift testing for a single page and small applications.
  • In templating: While Angular supports templating via dynamic HTML attributes, Backbone.js uses Underscore.js templates that aren’t fully-featured.
  • In Performance: Angular offers good performance for both small and large projects. Backbone.js may excel in small data sets or webpages, but is not recommended for larger webpages or data sets since it doesn’t have a data binding process.
  • In DOM: The focus of Angular JS is upon valid HTML and dynamic elements for rebuilding the DOM. On the contrary, Backbone.js follows the direct DOM manipulation approach.
  • In Data Binding: While Angular uses a two-way data binding process, Backbone.js has a simplistic API.
  • In Community Support: Since Angular is backed by Google, it has great community support and extensive documentation. Backbone.js has good community support, but lacks widely accessible documentation.
  • In architecture: Backbone.js makes use of the MVP architecture, while Angular works on the MVC architecture. Therefore, it makes use of two-way data binding for application activity.

Main Angular technical questions

Then, you must face some more technical stuff. You must also be prepared to do some coding if needed.

What are the building blocks of Angular?

There are 9 building blocks in an Angular application:

  • Components:  controls one or more views. Every Angular application has at least one root component inside the main module, known as the root module.
  • Data Binding: how parts of a template coordinate with parts of a component, added to the template HTML.
  • Dependency Injection: to provide required dependencies to new components. Dependency injection supply fully-formed dependencies required by a new instance of a class.
  • Directives: responsible for instructing Angular about how to transform the DOM when rendering a template.
  • Metadata: They tell Angular how to process a class.
  • Modules: AKA NgModules, a module is an organized block of code with a specific set of capabilities, within a specific application domain or a workflow.
  • Routing: responsible for interpreting a browser URL as an instruction to navigate to a client-generated view.
  • Services: A broad category of anything ranging from a value and function to a feature, Service is a class with a well-defined purpose.
  • Template: a form of HTML tags that lets Angular know that how it is meant to render the component.

What is Data Binding?

Data binding is the way to connect application data with the DOM (Data Object Model). There are 3 ways to do so:

  • Event Binding: The application responds to user input in the target environment.
  • Property Binding: Interpolates values computed from application data into the HTML.
  • Two-way Binding:  Changes made in the application state are reflected in the view and vice-versa. The ngModel directive is used for achieving this.

Define the ng-content Directive

Common HTML elements have content between tags. In Angular, the ng-content Directive is used to build reusable components.

What is a “service” in Angular?

Services in Angular are Singleton objects instantiated only once during the lifetime of an application. In an Angular service are methods that will maintain the data during the life of an application, to organize and share business logic, data and functions or models with several components of an Angular application.

In Angular, what is string interpolation?

Also calle “moustache syntax”, string interpolation in Angular is a special syntax that uses template expressions to display the component data, enclosed in double curly braces i.e. {{ }}.

Within the curly braces, we may execute JavaScript expressions and embed the output into the HTML code. These expressions are updated and registered as a part of the digest cycle.

What is Angular Authentication and Authorization?

On the server, there is an authenticate API that receives the user login credentials. Then, post server-side validation of the credentials is returned in a JWT (JSON Web Token). This token has information or attributes related to the current user, which is called authentication. When logging successfully, each user will have a different level of access, which is their authorization.

What is scope hierarchy in Angular?

Scope hierarchy in Angular is how the scope objects are organized into a hierarchy, used by views. It has a root scope that may contain one or several scopes, called child scopes.

Each view has its own scope. Then, variables set by a view’s view controller will remain hidden to others.

Define the concept of templates in Angular

Templates in Angular are written with HTML with Angular-specific attributes and elements. Then, combined with information from the controller and model, are rendered to cater the user with the dynamic view.

In Angular, what is the difference between an Annotation and a Decorator?

Annotations are used to create an annotation array, being a metadata set of the class using the Reflect Metadata library. Decorators are design patterns used to separate decoration or modification of some class, without changing the original source code.

What are directives in Angular?

Directives allow an Angular developer to write new, application-specific HTML syntax, as functions executed by the Angular compiler. Directives can be of Attribute, Component or Structural.

What is Angular Material?

Angular Material is a UI component library that helps in creating attractive, fully functional and consistent web pages and web applications.

What is AOT (Ahead-Of-Time) Compilation?

Each Angular app is compiled internally, when the Angular compiler takes in the JS code, compiles it and then produces new JS code only once per occasion per user.

Always be prepared

Those are only some of the questions that you may face in an Angular Interview, but of course each company has a different set. Be straightforward and honest if they ask something that you don’t know, because you don’t want to pretend to be a know-it-all.

So, good luck and all the very best!

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