Angular Interview Question Set 5

Categories: Angular

What is the role of SPA in Angular?

SPA stands for Single Page Application. This technology only maintains one page, index.HTML, even when the URL changes constantly. SPA technology is easy to build and extremely fast in comparison to traditional web technology.


Explain different kinds of Angular directives.

There are three kinds of directives in Angular. Let’s discuss them:

Components: A component is simply a directive with a template. It is used to define a single piece of the user interface using TypeScript code, CSS styles, and the HTML template. When we define a component, we use the component decorated with the @ symbol and pass in an object with a selector attribute. The selector attribute gives the Angular compiler the HTML tag that the component is associated with so that, now, when it encounters this tag in HTML, it knows to replace it with the component template.

Structural: Structural directives are used to change the structure of a view. For example, if we wish to show or hide some data based on some property, we can do so by using the ngIf directive, or if we wish to add a list of data in the markup, we can use *ngFor, and so on. These directives are called structural directives because they change the structure of the template.

Attribute: Attribute directives change the appearance or behavior of an element, component, or another directive. They are used as the attributes of elements. Directives such as ngClass and ngStyle are attribute directives.



What are the different types of compilers used in Angular?

In Angular, we use two different kinds of compilers:

Just-in-time (JIT) compiler

Ahead-of-time (AOT) compiler

Both these compilers are useful but for quite different purposes. The JIT compiler is used to compile TypeScript to JavaScript as our browsers cannot understand TypeScript but only JavaScript. This compilation step is done in a development environment, i.e., when less time is needed to be spent on compilation and more in development to quickly iterate over features. The JIT compiler is used when we use ng serve or ng build command to serve the app locally or create an uncompressed build of the entire codebase.



What is the purpose of the common module in Angular?

In Angular, the common module that is available in the package @angualr/common is a module that encapsulates all the commonly needed features of Angular, such as services, pipes, directives, etc. It contains some sub-modules as well such as the HttpClientModule, which is available in the @angular/common/http package. Because of the modular nature of Angular, its functionalities are stored in small self-contained modules, which can be imported and included in our projects if we need these functionalities.



What are the differences between AngularJS and Angular?

AngularJS is the previous version of Angular, which is a complete rewrite, i.e., there are several differences between the two that we can highlight.


Architecture: AngularJS supports the MVC architecture in which the model contains the business logic; the view shows the information fetched from the models, and the controller manages interactions between the view and the model by fetching data from the model and passing it to the view. On the other hand, Angular architecture is based on components where instead of having separate pieces for logic, presentation, etc., we now have a single self-contained piece of the user interface that can be used in isolation or included in a big project.

Language: In AngularJS, we could only use JavaScript. However, in Angular, we can use both TypeScript and JavaScript.

Mobile support: In AngularJS, we do not get mobile browser support out of the box, but in Angular, we do get mobile support for all popular mobile browsers.



What are the differences between Angular expressions and JavaScript expressions?

Angular expressions and JavaScript expressions are quite different from each other as, in Angular, we are allowed to write JavaScript in HTML, which we cannot do in plain JavaScript. Also, all expressions in Angular are scoped locally. But, in JavaScript, these expressions are scoped against the global window object. These differences, however, are reconciled when the Angular compiler takes the Angular code we have written and converts it into plain JavaScript, which can then be understood and used by a web browser.



What is server-side rendering in Angular?

In a normal Angular application, the browser executes our application, and JavaScript handles all the user interactions. However, because of this, sometimes, if we have a large application with a big bundle size, our page’s load speed is slowed down quite a bit as it needs to download all the files, parse JavaScript, and then execute it. To overcome this slowness, we can use server-side rendering, which allows us to send a fully rendered page from the server that the browser can display and then let the JavaScript code take over any subsequent interactions from the user.



 What is Angular Universal?

Angular Universal is a package for enabling server-side rendering in Angular applications. We can easily make our application ready for server-side rendering using the Angular CLI. To do this, we need to type the following command:

ng add @nguniversal/express-engine



 What is the difference between interpolated content and the content assigned to the innerHTML property of a DOM element?

Angular interpolation happens when in our template we type some JavaScript expression inside double curly braces ‘{{ someExpression() }}’. This is used to add dynamic content to a web page. However, we can do the same by assigning some dynamic content to the innerHTML property of a DOM element. The difference between the two is that, in Angular, the compiler always escapes the interpolated content, i.e., HTML is not interpreted, and the browser displays the code as it is with brackets and symbols, rather than displaying the output of the interpreted HTML. However, in innerHTML, if the content is HTML, then it is interpreted as the HTML code.



What are HttpInterceptors in Angular?

HttpInterceptors are part of the @angular/common/HTTP module and are used to inspect and transform HTTP requests and HTTP responses as well. These interceptors are created to perform checks on a request, manipulate the response, and perform cross-cutting concerns, such as logging requests, authenticating a user using a request, using gzip to compress the response, etc. Hopefully, these Angular interview questions in 2021 have helped you get a better grasp of Angular as a framework, as well as its various features and capabilities.

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