Angular Interview Questions for Freshers

Software Development | Design, Digital, Technology | Oct 28,2021 | By Nikita Dhiman

As a framework for constructing front-end web applications, Angular has gained in popularity. During your interview, this list of Angular interview questions will surely come in helpful.

1.What exactly is Angular?

ANS:Angular is a development platform and application design framework for creating complex and efficient single-page apps. This page covers Angular 2.0 and subsequent versions, including Angular 11, Angular 10, Angular 9, Angular 8, Angular 7, and so forth. The moniker AngularJS is used for Angular 1.x versions.

2.What distinguishes Angular from AngularJs?

ANS:Both Angular and AngularJS are open source JavaScript-based frameworks for developing single-page web applications (SPAs). AngularJS was the term given to Angular versions 1.x, whereas Angular 2.0 and subsequent were simply referred to as Angular.

3.What are the benefits of AngularJS over Angular?

ANS:Angular is a free and open-source application design framework and platform for developers that uses typescript. It has a lot of benefits. For bigger apps, Angular provides superior architectural support. TypeScript has OOPS capabilities as well as improved type verification. Support for mobile devices is a useful feature. Routing is easier to set up. Dependency injection is built-in. Provide the ability to develop code in a variety of languages, such as typescript, ES5, and Dart. It's simple to upgrade to newer versions. From Angular 4.0 forward, AOT compilation is supported.

4.NgModules vs. JavaScript Modules: What's the Difference?

ANS:In the following respects, NgModules vary from JavaScript modules. Because the Angular compiler only understands defined classes, NgModule only binds to those. Angular modules employ the declaration array to contain all member class files, whereas JavaScript modules specify all member classes in a single large file. NgModules exports just the classes that it declares and imports from other modules, not all of them. NgModules can offer services to the entire application by adding providers to its providers list, but JavaScript modules cannot.

5.In Angular, what is the host view?

ANS:When a component is built, it is immediately linked to a single view known as the host view.

6.What is Angular Data Binding? Explain the concept of two-way data binding.

ANS:Data binding is a technique for sharing data between a component class and its view template. Angular supports two-way data binding, which means component properties may be used in views for data, and any changes to the view should be reflected in the component's properties.

7.In Angular, what are Interpolation and Template Expressions?

ANS:The simplest way to bind a component property in the view is to use interpolation. You place the property in the double curly brackets 'property=name' in Interpolation. When a Template expression is enclosed in double curly brackets and yields a value such as 1+1, the result is 2. An expression is the right side component of the '=' operator in Property binding.

8.What are angular's lifecycle hooks?

ANS:Angular controls the lifecycle of components and directives. Before unloading, Angular generates and renders the components, detects whether their data bound attributes change, and destroys them. Angular generates components by invoking its function Object() { [native code] } and then following the lifecycle hooks in the order listed below. When Angular resets data bound properties, ngOnChanges() is invoked. ngOnInit() is used to establish data bound properties and initialise the directive or component. When angular's own modifications aren't recognised, ngDoCheck() is utilised to capture such changes. ngAfterContentInit() ngAfterContentChecked() ngAfterViewInit() ngAfterViewChecke()

9.In Angular, what are pipes?

ANS:A Pipe is a data transformation tool that allows you to change data from your data input to the required output. If you receive some lower case data from the back end and want to display it in upper case, you can use the Angular built-in pipe 'uppercase'. You may also use angular to make your own own pipelines.

10.What exactly is the AOT compilation? Alternatively, what is the distinction between JIT and AOT?

ANS:Your application may be compiled in one of two ways using Angular. JIT - Just-in-Time (JIT) builds the programme in the browser at runtime. In Angular, the default compiler is JIT. Your application will be compiled when you execute ng-build or ng-server. It builds the application ahead-of-time (AOT) at build time. Before browsers start downloading JavaScript code, the AOT compiler turns all HTML and TypeScript code into JavaScript code. It speeds up rendering. AOT has several advantages, which are listed below. Browsers get pre-compiled code and do not wait for compilation that results in faster Rendering. It reduces the size of Angular framework as there is no need to download the compiled code. Errors can be detected earlier during the build phase only. AOT reduces the chances of injection attacks as it compiles the code long before they are sent to the client.

AOT improves the number of asynchronous resource requests as it inlines the external HTML templates and styles.

11.What are the Angular Services?

ANS:Angular services are classes that have a clear purpose. Services offer functionality in a modular format that may be utilised across several components. Services can be used to exchange data across components. You may improve the efficiency of your components by outsourcing some functionality code to services, such as fetching data from the server and applying validation criteria. You may make your code reusable to any component by designating it as a service. Using the @Injectable decorator, you may establish a service.

12.In Angular, how do you make a service a singleton?

ANS:As seen below, there are two ways to make a service a singleton. The first method is to inject the service in root by setting the @Injectable decorator's 'providedIn' property to 'root'. The second option is to include the service just in AppModule or in a module that is only imported in AppModule.

13.In Angular, what is the provider?

ANS:Dependency injection is used in Angular to inject service dependencies. A Provider acts as an educator for the dependency injection system to resolve dependencies. When you create a service, it includes a default @Injectable decorator with a default property 'providedIn' that creates the service provider.

14.What is the purpose of dependency injection in Angular?

ANS:DI stands for Dependency Injection and is a design pattern. To improve the efficiency and modularity of Angular applications, Angular provides its own dependency injection. A dependency is an object or class that another class requires to complete its activities. For example, to execute user actions, a 'UserComponent' requires a 'UserService.' When the Angular DI framework instantiates the class or component, it injects the dependencies. In Angular, using the @Injecible decorator to establish a service is required. You must provide providers in order for dependency injection to inject the service.

15.What exactly is the RxJS library?

ANS:RxJS (Reactive Extensions for JavaScript) is a library for asynchronous and event-based or callback-based programmes that leverages observable sequences. The RxJS library features a single core type called 'Observable,' as well as satellite kinds such (Observer, Schedulers, Subjects). Many operators are available in RxJS to support the capabilities listed below. To map to many sorts. Iteration Filter Multiple streams are combined into one. Convert current code into observables to execute asynchronous activities.

16.In Angular, what are the observables?

ANS:Observables are used in Angular to perform several common asynchronous activities, as shown below. To transfer observable output data from child to parent components, custom events are needed. HTTP Modules employ observables to manage Ajax requests and replies. Forms and Router Modules employ observables to listen for and respond to user-input events.

17.In Angular, what is the difference between Promises and Observables?

ANS:Most of the time, Observables are compared to Promises, however there are some distinctions between them, as shown below. Observables are declarative, which implies that execution begins only when you subscribe to them, whereas Promises begin execution only when they are created. Observables can return numerous values over time, whereas Promises only return one. While observables offer a variety of ways for performing changes, promises only have the '.then' function. Promises send errors to their children, whereas the subscribe method of an Observable handles errors well.

18.What's the deal with the route guards?

ANS:A user can use the programme from any location at any time, but you may want to restrict user access for the reasons listed below. Login is required for all users. Before the user navigates, you'd like to preserve some information. You wish to give the user permission. You might request that the user delete any outstanding updates. There are also additional causes. Angular includes the idea of guards, which may be applied to routes to manage certain cases. The return value of guard can be used to affect the behaviour of the router, as seen below. If the value is true, the navigation will proceed. Navigation comes to a halt if the value is false. If the value is UrlTree, fresh navigation for the returned UrlTree will begin.

19.In Angular, what is a Root Module?

ANS:Every Angular application has at least one module, which you bootstrap to start the project. Root Module is the name of this module. When you build an angular application, one NgModule with the name AppModule is created by default as the root module.

20.Explain how feature modules are loaded in a lazy manner.

ANS:By default, all NgModules in Angular are eager loaded, which means they load as soon as the app does. However, lazy loading is recommended for big applications with several paths. Lazy loading is a design technique that loads modules only when they are needed. Because the initial size of the bundle is less, it reduces the application's loading speed.

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