Top 30 Angular Interview Questions and Answers

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22 Jul 2022

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If you are willing to keep in your footstep in the development sector including the JavaScript programming language and want to move on to the Javascript frameworks learning, then the modern industry must need developers who know various in-demand frameworks. After learning different types of in-demand frameworks, you can gain knowledge and also get a better chance of bagging a high package job. Among all the most popular frameworks, Angular is in high demand today in the market. So, taking Angular Online training will not only improve your knowledge and skills but also able to make a better future in the development sector.

Previously web developers have mainly used jQuery and Vanilla JS to develop any dynamic website but according to the logic of one’s website grew, the code became more and more monotonous to maintain. For any complex logic applications, developers had to put an extra effort to maintain the separation of concerns for the app. But, jQuery did not provide facilities for data handling across views.

So, to overcome all such issues client-side framework Angular came into the scenario which made the life of the developer as well as the organization easier by handling the separation of concerns and dividing code into smaller bits of information. Today it is in high demand among various industries across the world. So, to make yourself ready in Angular and to get a good job in Angular, you need to prepare yourself for the interview and take training along with the Angular Interview Question Answer Pdf file to crack the interview.

What is Angular?

Angular is a JavaScript-based framework developed by Google. Angular allows developers to build applications for browsers, mobile, and desktops using web technologies like HTML, CSS, and JavaScript.

Angular2+ is different from Angular1.x and it is completely re-written from scratch using Typescript. At the time of writing this, book the latest version of Angular was 13 which was released in Nov 2021.
One of the primary features of the Angular framework is that it uses TypeScript as a primary programming language. But at the same time, it is also possible to create Angular applications using other different languages such as Dart or JavaScript. But having the features like strict type checking, the TypeScript is still the primary language.
Explain the evolution history of Angular?

The evolutionary history of Angular is given below –
What are the differences between Angular2+ and Angular 1.x?

There are the following differences between Angular2+ and Angular 1.x are given below:

Angular 2+
Angular 1.x

Based on components
Based on controller and scope

Improved DI
Supports DI

Mobile First
Not built with mobile first

Supports ES5/6, TS, or Dart
Supports ES5/6 or Dart

Supports Angular CLI
Doesn’t have CLI

The class is the only way to define services in Angular2
factory, service, provider, value, and constant are used for services

Runs on client-side & server-side
Runs on only client-side

bootstrapModule() function is used to initialize
ng-app and angular.bootstrap() function are used to initialize

Supports Pipe
Support filters

Supports camelCase and PascalCase syntaxes likengModel, ngForm and NgForm
Supports spinal-case and camelCase syntaxes like ng-model, ng-class, and ngModel

Use Html DOM elements properties and events
Uses its directives like ng-click, ng-show, ng-src, etc.

Use () for events and [] for attributes
Doesn’t support () and [] based syntax
Why uses Angular?

There are multiple reasons to use Angular over other front-end frameworks which are listed below.
- Angular is a full-featured Single Page Application (SPA) framework
- The product of Google and completely open-source
- Follows MVC (Model View Controller) architecture
- Simple Dependency Injection implementation
- It supports Typescript and ES6 standard
- Able to create a re-usable component, modules, routes
- Supports to enable testing using jasmine and karma
- Great community support
Important fundamentals of Angular

Angular has a large number of features which makes it more useful than other front-end frameworks, below is the list of important features.
- Component
- Module
- Data bindings
- Services
- Dependency Injection
- Directives
- Templates
- Application Bootstrapping
- Navigation or Routing
- Native mobile development
  Angular Elements
  Angular Universal
What are the new features of Angular 7?

Recently Angular has released its newer version Angular 7, and with this version, we got several updates as well as the new features and these are listed below.
- CLI Prompt
- Angular Elements
- Updates in Angular Material
- Virtual scrolling
- Drag and Drop
- Setting budgets
- Checking bundle size
- Ivy rendering engine
- Typescript 3.1 supports
How to update your app to Angular 7?

If you want to work on the latest version of Angular then we need to update our Angular CLI as well as Core angular packages by using the below command.
```
 ng update @angular/core @angular/cli
```
What is an Angular CLI?

Angular Command Line Interface is a command line tool that is used to create, initialize, scaffold, and manage the whole angular application. We can also use the Angular Console tool to work with the command line to generate or work with a different part of the Angular application, using CLI we can manage everything using commands.

Some of the frequently used Angular CLI commands are ng build, ng serve, ng add, ng generate, and other such commands which can be used to get started quickly with the Angular app.
You can find the complete details of Angular CLI and different commands in the CLI introduction part later on in this series.
What are the features of Angular CLI?

Angular CLI is a powerful command-line tool by which we can create new files, update the file, build and deploy the angular application and other features are available so that we can get started with Angular development within a few minutes.
- Packaging application and release for the deployment
- Testing an Angular app
- Bootstrapping Angular app
- Various code generation options for Component, Module, Class, Pipes, Services, Enums, and many other types are also supported.
- Running the unit test cases
- Build and deployment our Angular application
  
  Read More: 7 Tips to Optimize Your Angular App/Application
What is the Angular Console?

Angular CLI is a powerful tool and by using this we can develop an Angular application without following complex stuff. Angular Console is a way to achieve different command line features using a simple GUI which is a completely alternative to knowing all of the CLI commands. To download the GUI tool, you can get the executable file from here. And after downloading the tool, it will look like this.
What are the advantages of the Angular Console?

There are a few advantages and features provided by the Angular Console.
- Build CLI Commands visually
- Internal terminal for the output
- Import the existing Angular project
- Trivial code generation
- Run the custom NPM scripts
- Install various extensions
How to get the version of Angular CLI?

To get the current version of the Angular CLI, we can use the below command.
```
 ng –version
```
After running the above command, we will get the output like this.
How to specify the type of stylesheet using the command?

Angular 7 provides the CLI prompt where we can choose stylesheet type from the available option, but for an older version, CSS was the default format for styling the pages. But for that, we can use the additional flag --style to specify any other supported stylesheet type than CSS, below is a simple example by which we can use a specific stylesheet format while creating a new Angular app.
```
 ng new <project_name>--styles <type>
```
Example
```
 ng new ngDemo --styles scss
```
After running the above command, now our default stylesheet format will be SCSS, not the CSS, this is how we can change the stylesheet type.
What is a Component in Angular?

Components are the basic building block of an Angular application. An Angular component mainly contains a template, class, and metadata. It is used to represent the data visually. A component can be thought of as a web page. An Angular component is exported as a custom HTML tag like as: <my-app></my-app>.

When we create a new create an Angular app using CLI, it will create a default App component as the entry point of the application. To declare a class as a Component, we can use the Decorators and decorators to declare a component that looks like the below example.
```
 import{ Component } from'@angular/core';
 
 @Component({
 selector: 'my-app',
 template: `<h1>{{ message }}</h1>`,
 styleUrls: ['./app.component.css']
 })
 exportclassAppComponent {
 message = "Hello From Angular";
 }
```
For creating a component, we can use decorator @component like the above example. If we are using Angular CLI then a new component will be created using the below ng command.
```
ng generate component democomponent
```
What is the Template Expression?

Template expressions are the same expression that we use with JavaScript. But the difference is that we can use it within our Html template, so it looks like we are using JavaScript along with Html but keep in mind that not every JavaScript expression is supported like (new), (++) and (--). Let’s see a simple example of the mathematical calculation using template expression.
App.component.html
```
 <p>Addition : {{ 1 + 1 }}</p>
 <p>Subtraction : {{ 25 - 50 }}</p>
 <p>Multiplication : {{ 25 * 50 }}</p>
 <p>Division : {{ 25 / 50 }}</p>
```
Here we have used {{ }} brackets in order to use an expression within our template, and you can see the output like this.
What is Data Binding in Angular?

Data binding is one of the important core concepts which is used to do the communicate between the component and DOM. In other words, we can say that Data binding is a way to add/push elements into HTML Dom or pop the different elements based on the instructions given by the Component. There are mainly three types of data binding support in order to achieve the data bindings in Angular.
- One-way Binding (Interpolation, Attribute, Property, Class, Style)
- Event Binding
- Two-way Binding
Using these different binding mechanisms, we can easily communicate the component with the DOM element and perform various operations.
What is Interpolation?

Interpolation in Angular is used to show the property value from the component to the template or used to execute the expressions. Generally, interpolation can be used to execute the JavaScript expressions and append the result to the Html DOM. Another use of Interpolation is to print the data or we can say one-way data, which is coming from the component i.e. from a variable or the item of an array. And interpolation can be used to achieve Property binding as well by using curly braces {{ }}, let’s see a simple example.
App.component.ts
```
 myMessage: string = "Hello World";
```
App.component.html
```
 <p>{{ myMessage }}</p>
 <p>Total : {{ 25 + 50 + 75 + 100 }}</p>
```
In the same way, we can use interpolation to the different places or elements like the source of the image, values for the classes, and other users as well. The output will look like this.
What is Property Binding?

Property binding is generally used to show or update the value of the variables in the component and vice versa. We can also call it one-way data binding thus it is not used to update the two-way binding mechanism, and the value will be reflected at the component level. Let’s see the simple example by taking a simple string value from the component to the template.
App.component.ts
We are going to create a string variable with a default value like this.
```
 myMessage: string = "Hello World";
```
And to show this message into the template, we will use a {{ }} symbol which is called interpolation like this.
App.component.html
```
 <h1>{{ myMessage }}</h1>
```
Whenever we change the value of the myMessage variable, at that time it will be reflected in the template but not vice versa.
What is Directive in Angular?

The directive in Angular is a class with the (@) decorator and the duty of the directive is to modify the JavaScript classes, in other words, we can say that it provides metadata to the class. Generally, @Decorator changes the DOM whenever any kind of action happens and it also appears within the element tag. The component is also a directive with the template attached to it, and it has template-oriented features. The directive in Angular can be classified as follows.
1. Component Directive
2. Structural Directive
3. Attribute Directive
What is a Module in Angular?

The module in Angular is a very essential part of the application, which is used to organize our angular app in a distributive manner. Or we can say that Modules play an important role to structure our Angular application. Each Angular application must have one parent module which is called an app module and it contains the list of different items which are listed below.
- Components
- Service providers
- Custom modules
- Routing modules
- Pipes
  
  Module files group all of them into a single file; the same module will be useful for bootstrapping the application.
What is dependency injection in Angular?
Dependency injection (DI) is a significant application design pattern. In that, a class inquires for dependencies from external sources instead of creating them on its own. Moreover, Angular supports its dependency injection framework to resolve dependencies. Here, the dependencies include objects or services that a class has to perform its function. Hence, your services can rely on other services all over your application. When you go for Angular Training, you can learn in detail what dependency injection in Angular is.
How to opt from inline and external template files?

It is possible to store the template of your component in any of the two places. You can either define it inline through the ‘template’ property or define the template within a distinct HTML file. Subsequently, you can connect to it in the component metadata through the ‘templateUrl’ property of the decorator of the ‘@Component’ decorator.
The choice between separate HTML and inline relies on your preference, organization policy, and situation. However, usually, we utilize an inline template for a tiny part of code as well as an external template file for larger views.
How pure and impure pipe?

A pure pipe is called only when Angular identifies a modification in either the value or parameter passed to a pipe. For instance, any modifications to a primitive input value (Number, String, Symbol, Boolean) or a changed object reference (Array, Date, Object, Function).

An impure pipe is invoked for each change alteration cycle irrespective of whether the parameters or value modifies. Keep in mind that an impure pipe is called frequently; as frequently as each mouse-move or keystroke. The angular js training in Hyderabad will reinforce your base for Angular.
What is HttpClient? What are its benefits?

The majority of the Front-end applications carry out communication with backend services on HTTP protocol through fetch() API or XMLHttpRequest interface. Angular offers an easy client HTTP API i.e. ‘HttpClient’ that is dependent on top of the XMLHttpRequest interface. The corresponding client is accessible from @angular/common/http package. It can be imported into your root module as follows:

import { HttpClientModule } from '@angular/common/http';

The benefits of HttpClient are as follows:
- Comes with testability features
- Offers response objects and typed request
- Intercept request and response
- Supports streamlined error handling
- Supports Observalbe APIs
Explain the differences between promise and observable?

Observable is declarative, so computation does not begin until subscription so that they could be run anytime you require the result. On the other hand, Promise executes instantly on creation. Observable provides multiple values over time whereas Promise provides only one.

In Observable, Subscribe method is useful for error handling. It leads to centralized and expected error handling. On the other hand, Promise pushes errors to the child's promises.

Observable offers subscription and chaining to deal with complex applications. But Promise uses only .then() clause.
What are the constraints of metadata?

In Angular, you should write metadata with the below constraints:
- Write expression syntax inside the supported range of javascript features
- Only call the functions that are supported by the compiler
- The compiler could only reference symbols that are exported
- Decorated as well as data-bound class members should be public.
Such constraints can be identified when you go through Angular Tutorial.
What is the transition function?

The animation transition function is extensively used to mention the changes that take place between one state and another on a particular time cycle. It accepts 2 arguments. The first one accepts an expression that defines the direction amongst two transition states whereas the second one accepts an animate() function.

Below is an example of state transition from open to closed with a quarter second transition amongst states.

transition('open => closed', [

animate('250ms')

]),

Those thinking about how to become angular developers should clear all basic Angular concepts.
What is a platform in Angular?

A platform is a framework in which a specific Angular application executes. A web browser is a widely used platform for Angular applications. However, it could also be used in form of an operating system for a web server or mobile device. The runtime platform is given by @angular/platform-* packages. Such packages make sure the applications utilize @angular/core as well as @angular/common to implement in different environments.

Angular can be used in form of a platform-independent framework in various environments. It can use the platform-browser package when running in the browser. If you wish to Learn Angular Step by Step, the concept of the platform is important.
What are the new features found in Angular 6?

It is wise to stay updated with Angular 6 latest features when preparing for Angular Interview Questions pdf. Look at some latest features of Angular 6:
- Angular Elements: Allows conversion of Angular components into web components. Also, it embeds the same in a few non-Angular applications.
- RxJS 6: Angular 6 uses RxJS 6 internally.
- Tree Shakeable Provider: Angular 6 presents an innovative approach to directly registering a provider within the @Injectable() decorator. The same is achieved with the provided attribute.
- i18n (internationalization): Any Angular application can have “runtime i18n”; no need to build the application once per environment.
- Angular 6 moved from the modules referencing service to service by referencing the modules to make the Angular app compact in terms of size. The tree shaking is a build optimization step that tries to ensure that any unused code does not get used in the final application bundle.

Summary

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