Web Development

Top 100 Angular Interview Questions and Answers for 2024

Published: 23rd June, 2023

Arunav Goswami

Web Development Consultant at almaBetter

Ace your next tech interview with our comprehensive guide on top 100 Angular interview questions, covering essential topics from easy to advanced concepts.

Welcome to our comprehensive guide on the top 100 Angular interview questions! As one of the most popular and powerful web application frameworks, Angular has become a must-have skill for developers. Whether you are preparing for your first interview or are an experienced professional looking to brush up on your knowledge, this blog is designed to cater to your needs. We have carefully curated a list of questions that include both Angular JS interview questions for beginners and Angular interview questions for experienced developers. This resource will equip you with the confidence and expertise needed to tackle even the most challenging Angular-related questions during your job interviews. So, let's dive in and explore the world of Angular together!

Q.1. What are the differences between Angular decorator and annotation?

Solution: In Angular, decorators are design patterns that help in the modification or decoration of the respective classes without making changes in the actual source code.

Annotations, on the other hand, are used in Angular to build an annotation array. They use the Reflective Metadata library and are a metadata set of the given class.

Q.2. What is an AOT compilation in Angular?

Solution: The AOT (ahead-of-time) compiler in Angular converts Angular HTML and TypeScript code into JavaScript code during the build phase, which makes the rendering process much faster. This compilation process is needed since Angular uses TypeScript and HTML code. The compiler converts the code into JavaScript, which can then be effectively used by the browser that runs our application.

Q.3. What are dynamic components?

Solution: Dynamic Components in the Angular framework are the components that help in building large-scale applications easily. Dynamic components are usually instantiated and placed in the application at runtime.

Q.4. What are modules in Angular?

Solution: A module is a logical boundary of our application. It is used to encapsulate code dealing with a specific aspect of the application, such as routing, HTTP, validation, etc. The main reason why modules are used is to enhance application composability. For example, if we wish to implement validation logic using different libraries, then for the one we have already implemented, we can create a new validation module and replace the current one with the new one, and our application would work just the same. In Angular, we create a module using the NgModule decorator.

Q.5. What are services in Angular?

Solution: A service in Angular is a term that covers broad categories of functionalities. A service is any value, function, or feature that an app needs. A service is typically used to accomplish a very narrow purpose, such as HTTP communication, sending data to a cloud service, decoding some text, validating data, etc. A service does one thing and does it well. It is different from a component as it is not concerned with HTML or any other kind of presentation logic. Normally, a component uses multiple services to accomplish multiple tasks.

Q.6. What are lifecycle hooks in Angular?

Solution: When building an Angular app, there will be times when we need to execute some code at some specific event—such as when a component is initialized or displayed on the screen or when the component is being removed from the screen. This is what lifecycle hooks are used for. For example, if we have some event listener attached to an HTML element in a component, such as a button click or form submission, we can remove that event listener before removing the component from the screen, just like we can fetch some data and display it on the screen in a component after the component is loaded on the screen. To use a lifecycle hook, we can override some methods on a component, such as ngOnInit or ngAfterViewInit. These methods, if available on a component, will be called by Angular automatically. This is why these are called lifecycle hooks.

Q.7. What are pipes in Angular?

Solution: When we are trying to output some dynamic data in our templates, we may sometimes need to manipulate or transform the data before it is put into our templates. Though there are several ways of doing that, in Angular, using pipes is the most preferred way. A pipe is just a simple function that we can use with expressions in our templates.

Pipes are extremely useful as we can use them throughout our application after declaring them just once and registering them with the Angular framework. Some of the most common built-in pipes in Angular are UpperCasePipe, LowerCasePipe, CurrencyPipe, etc.

Q.8. How are observables different from promises?

Solution: Although both promises and observables are used to handle asynchronous requests in JavaScript, they work in very different ways. Promises can only handle a single event at a time, while observables can handle a sequence of asynchronous events over a period of time. Observables also provide us with a wide variety of operators that allow us to transform data flowing through these observables with ease.

A promise is just a way to wrap asynchronous operations so that they can be easily used, while an observable is a way to turn asynchronous operations into a stream of data that flows from a publisher to a subscriber through a well-defined path with multiple operations transforming the data along the way.

Q.9. What is bootstrapping?

Solution: Angular bootstrapping, in simple words, allows professionals to initialize or start the Angular application. Angular supports both manual and automatic bootstrapping. Let’s briefly understand the two.

Manual bootstrapping: It gives more control to professionals with regard to how and when they need to initialize the Angular app. It is extremely useful in places where professionals wish to perform other tasks and operations before Angular compiles the page.

Automatic bootstrapping: Automatic bootstrapping can be used to add the ng-app directive to the application’s root, often on the tag if professionals need Angular to bootstrap the application automatically. Angular loads the associated module once it finds the ng-app directive and further, compiles the DOM.

Q.10. What do you mean by dependency injection?

Solution: Dependency injection (DI) in Angular is a software design pattern in which the objects can be passed in the form of dependencies instead of hard-coding them in the respective components. This concept is extremely handy when it comes to separating the object logic creation from its consumption.

The function ‘config’ uses DI, which needs to be configured to load the module to retrieve the application elements. Besides, this feature allows professionals to change dependencies based on necessities.

Q.11. Describe Angular authentication and authorization.

Solution: The login details of a user are given to an authenticated API available on the server. Once the credentials are validated by the server, it returns a JSON web token (JWT), which includes attributes and the data of the current user. Further, the user is easily identified using JWT, and this process is known as authentication.

After logging in, users have various types and levels of access—some can access everything, while others may have restrictions from some resources. Authorization determines the access level of these users.

Q.12. What is the digest cycle process in Angular?

Solution: The digest cycle in Angular is the process in which the watch list is monitored to track changes in the watch variable value. In each digest cycle, there is a comparison between the present and the previous versions of the scope model values.

Q.13. What is Angular Router?

Solution: Routing in a single-page frontend application is the task of responding to the changes in the URL made by adding and removing content from the application. This is a complicated task as we first need to intercept a request that changes the browser’s URL as we do not wish for the browser to reload. Then, we need to determine which content to remove and which content to add, and finally, we have to change the browser’s URL as well to show the user the current page they are on.

As we can see, this can be very difficult to implement, especially in multiple applications. That is why Angular comes with a full routing solution for a single-page application. In this, we can define routes with matching components and let Angular handle the routing process.

Q.14. What is REST?

Solution: REST in Angular stands for Representational State Transfer. It is an API that works on the request of HTTP. Here, the requested URL points to the data that has to be processed, after which an HTTP function is used to identify the respective operation that has to be performed on the data given. The APIs that follow this method are referred to as RESTful APIs.

Q.15. Explain Angular CLI.

Solution: Angular CLI is otherwise known as Angular command-line interface. Angular supports CLI tools that give professionals the ability to use them to add components, deploy them instantly, perform testing, and many such functions.

Q.16. What is a schematic?

Solution: Schematics are template-based code generators that enable complex logic. It is usually packaged into collections and installed with npm. The aim of schematics is to transform a software project by generating or modifying codes.

Q.17. What is HttpClient, and what are its benefits?

Solution: HttpClient is an Angular module used for communicating with a backend service via the HTTP protocol. Usually, in frontend applications, for sending requests, we use the fetch API. However, the fetch API uses promises. Promises are useful, but they do not offer the rich functionalities that observables offer. This is why we use HttpClient in Angular as it returns the data as an observable, which we can subscribe to, unsubscribe to, and perform several operations on using operators. Observables can be converted to promises, and an observable can be created from a promise as well.

Q.18. What is multicasting in Angular?

Solution: In Angular, when we are using the HttpClient module to communicate with a backend service and fetch some data, after fetching the data, we can broadcast it to multiple subscribers, all in one execution. This task of responding with data to multiple subscribers is called multicasting. It is specifically useful when we have multiple parts of our applications waiting for some data. To use multicasting, we need to use an RxJS subject. As observables are unicast, they do not allow multiple subscribers. However, subjects do allow multiple subscribers and are multicast.

Q.19. What is a directive in Angular?

Solution: A directive in Angular is used to extend the syntax and capabilities of a normal HTML view. Angular directives have special meanings and are understood by the Angular compiler. When Angular begins compiling the TypeScript, CSS, and HTML files into a single JavaScript file, it scans through the entire code and looks for a directive that has been registered. In case it finds a match, then the compiler changes the HTML view accordingly.

Angular is shipped with many directives. However, we can build our directives and let Angular know what they do so that the compiler knows about them and uses them during the compilation step.

Q.20. What are the differences between Angular expressions and JavaScript expressions?

Solution: 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.

Q.21. What is server-side rendering in Angular?

Solution: 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.

Q.22. What are HttpInterceptors in Angular?

Solution: 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. These frequently asked questions have been created to better understand the kinds of questions asked in interviews, so they will help you understand Angular interviews and Angular as a framework. These Angular interview questions with their answers might have whetted your appetite for learning more about the framework. They will surely help you to ace your next job interview.

Q.23. How does one share data between components in Angular?

Solution: There is not one but various methods to share data between components in Angular. They are mentioned below:

Parent to Child: via Input

Child to Parent: via Output() and EventEmitter

Child to Parent: via ViewChild

Unrelated Components: via a Service

Q.24. What is folding?

Solution: In Angular, it might be possible while generating the code that some of the non-exported members are folded. This is called Folding, i.e., the process in which the evaluation of an expression is done by the collector, and the result is recorded in the .metadata.json, which is known as Folding.

Q.25. What is NoopZone?

Solution: NoopZone helps Angular figure out and know when to trigger the change detection. However, in the event that Angular needs to be used without a zone, the NoopZone, too needs to be configured.

Q.26. What are macros?

Solution: A Macros is a portion of a  programming code that helps in the automation of routine tasks. It usually runs in an Excel environment. In Angular, Macros is supported in the form of functions, static methods, etc.

Q.27. What is the purpose of the common module in Angular?

Solution: 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.

Q.28. What are the different types of compilers used in Angular?

Solution: In Angular, we use two different kinds of compilers:

  1. Just-in-time (JIT) compiler
  2. Ahead-of-time (AOT) compiler

Q.29. What is the browser support of Angular Elements?

Solution: Since Angular is built on the latest web platform standards, Angular elements are supported by Chrome, Edge (Chromium-based), Firefox, Opera, Safari, and other currently existing browsers via polyfills. Polyfills enable the running of full Angular applications.

Q.30. What is the role of SPA in Angular?

Solution: 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 compared to traditional web technology.

Q.31. What will happen if you do not supply a handler for the observer?

Solution: When a handler is not supplied to a notification type, the observer automatically ignores the notifications of that type and the observer instance publishes value only when it is subscribed to.

Q.32. What do you mean by string interpolation?

Solution: String interpolation in Angular, also known as the mustache syntax, only allows one-way data binding. It is a special syntax that makes use of double curly braces {{}} so that it can display the component data. Inside the braces are the JavaScript expressions that Angular needs to execute to retrieve the result, which can further be inserted into the HTML code. Moreover, as part of the digest cycle, these expressions are regularly updated and stored.

Q.33. What do you mean by data binding?

Solution: Data binding is among the most important and powerful features that help in establishing communication between DOM and the component. It makes the defining process of interactive applications simple, as you no longer need to panic about data pushing or pulling between the component and the template.

Q.34. What is content projection?

Solution: In Angular, Content projection refers to a pattern where you can insert or project the content you want to use inside a different component. For example, consider a Card component that can accept the content provided by another component.

Q.35. What are template expressions?

Solution: A template expression in Angular is an expression that is represented in double curly braces ‘{{ }}’ and produces a value. The template expression is executed by Angular and is assigned to a property of a binding target. Now, the binding target can be any of these- an HTML element, a directive, or even a component.

Q.35. What is two-way data binding in Angular?

Solution: Data sharing between a component class and its template is referred to as two-way data binding. If you alter data in one area, it will immediately reflate at the other end. This happens instantly and automatically, ensuring that the HTML template and TypeScript code are always up to date. Property binding and event binding are coupled in two-way data binding.

Q.36. What are Decorators and their types in Angular?

Solution: Decorators are a fundamental concept in TypeScript, and because Angular heavily relies on TypeScript, decorators have become an important element of Angular as well.

Decorators are methods or design patterns that are labeled with a prefixed @ symbol and preceded by a class, method, or property. They enable the modification of a service, directive, or filter before it is utilized. A decorator, in essence, provides configuration metadata that specifies how a component, class, or method should be processed, constructed, and used at runtime. Angular includes a number of decorators which attach various types of metadata to classes, allowing the system to understand what all these classes signify and how they should function.

Types of decorators:

  1. Method Decorators: Method decorators, as the name implies, are used to add functionality to the methods defined within our class.
  2. Class Decorator: Class Decorators are the highest-level decorators that determine the purpose of the classes. They indicate to Angular that a specific class is a component or module. And the decorator enables us to declare this effect without having to write any code within the class.
  3. Parameter Decorator: The arguments of your class constructors are decorated using parameter decorators.
  4. Property Decorator: These are the second most popular types of decorators. They enable us to enhance some of the properties in our classes.

Q.37. What are pure Pipes?

Solution: These are pipelines that only employ pure functions. As a result, a pure pipe does not employ any internal state, and the output remains constant as long as the parameters provided remain constant. Angular calls the pipe only when the parameters being provided change. A single instance of the pure pipe is utilized in all components.

Q.38. What are impure pipes?

Solution: Angular calls an impure pipe for each change detection cycle, independent of the change in the input fields. For each of these pipes, several pipe instances are produced. These pipes' inputs can be altered.

By default, all pipelines are pure. However, as demonstrated below, you can specify impure pipes using the pure property.

Q.39. What is Eager and Lazy Loading?


Loading: The eager loading technique is the default module-loading strategy. Eager-loading feature modules are loaded before the program begins. This is primarily utilized for small-scale applications.

Lazy Loading: Lazy loading loads the feature modules dynamically as needed. This speeds up the application. It is utilized for larger projects where all of the modules are not required at the start.

Q.40. What does Angular Material means?

Solution: Angular Material is a user interface component package that enables professionals to create a uniform, appealing, and fully functioning websites, web pages, and web apps. It does this by adhering to contemporary web design concepts such as gentle degradation and browser probability.

Q.41. What is transpiling in Angular?

Solution: Transpiling is the process of transforming the source code of one programming language into the source code of another. Typically, in Angular, this implies translating TypeScript to JavaScript. TypeScript (or another language like as Dart) can be used to develop code for your Angular application, which is subsequently transpiled to JavaScript. This occurs naturally and internally.

Q.42. What are HTTP interceptors?

Solution: Using the HttpClient, interceptors allow us to intercept incoming and outgoing HTTP requests. They are capable of handling both HttpRequest and HttpResponse. We can edit or update the value of the request by intercepting the HTTP request, and we can perform some specified actions on a specific status code or message by intercepting the answer.

Q.43. What is Change Detection, and how does the Change Detection Mechanism work?

Solution: The process of synchronizing a model with a view is known as Change Detection. Even when utilizing the ng Model to implement two-way binding, which is syntactic sugar on top of a unidirectional flow. Change detection is incredibly fast, but as an app's complexity and the number of components increase, change detection will have to do more and more work.

Change Detection Mechanism-moves only ahead and never backward, beginning with the root component and ending with the last component. This is what one-way data flow entails. The tree of components is the architecture of an Angular application. Each component is a child, but the child is not a parent. A $digest loop is no longer required with the one-way flow.

Q.44. What happens when you use the script tag within a template?

Solution: Angular detects the value as unsafe and sanitizes it automatically, removing the script tag but retaining safe material such as the script tag's text content. This reduces the potential for script injection attacks. If you continue to use it, it will be disregarded, and a warning will display in the browser console.

Q.45. When to use a directive?

Solution: Consider an application where multiple components need to have similar functionalities. The norm thing to do is by adding this functionality individually to every component but, this task is tedious to perform. In such a situation, one can create a directive having the required functionality and then, import the directive to components that require this functionality.

Q.46. What is interpolation?

Solution: Interpolation is a special syntax that Angular converts into property binding. It’s a convenient alternative to property binding. It is represented by double curly braces({{}}). The text between the braces is often the name of a component property. Angular replaces that name with the string value of the corresponding component property.

Q.47. What is the difference between pure and impure pipe?

Solution: A pure pipe is only called when Angular detects a change in the value or the parameters passed to a pipe. For example, any changes to a primitive input value (String, Number, Boolean, Symbol) or a changed object reference (Date, Array, Function, Object). An impure pipe is called for every change detection cycle no matter whether the value or parameters change. i.e., An impure pipe is called often, as often as every keystroke or mouse move.

Q.48. What are observables?

Solution: Observables are declarative which provide support for passing messages between publishers and subscribers in your application. They are mainly used for event handling, asynchronous programming, and handling multiple values. In this case, you define a function for publishing values, but it is not executed until a consumer subscribes to it. The subscribed consumer then receives notifications until the function completes, or until they unsubscribe.

Q.49. What are custom elements?

Solution: Custom elements (or Web Components) are a Web Platform feature that extends HTML by allowing you to define a tag whose content is created and controlled by JavaScript code. The browser maintains a CustomElementRegistry of defined custom elements, which maps an instantiable JavaScript class to an HTML tag. Currently, this feature is supported by Chrome, Firefox, Opera, and Safari, and is available in other browsers through polyfills.

Q.50. What are the various kinds of directives?

Solution: There are mainly three kinds of directives:

  1. Components — These are directives with a template.
  2. Structural directives — These directives change the DOM layout by adding and removing DOM elements.
  3. Attribute directives — These directives change the appearance or behavior of an element, component, or another directive.

Q.51. Do we always need a Routing Module?

Solution: No, the Routing Module is a design choice. You can skip the routing Module (for example, AppRoutingModule) when the configuration is simple and merge the routing configuration directly into the companion module (for example, AppModule). But it is recommended when the configuration is complex and includes specialized guard and resolver services.

Q.52. What is JIT?

Solution: Just-in-Time (JIT) is a type of compilation that compiles your app in the browser at runtime. JIT compilation was the default until Angular 8, now, the default is AOT. When you run the ng build (build only) or ng serve (build and serve locally) CLI commands, the type of compilation (JIT or AOT) depends on the value of the aot property in your build configuration specified in angular.json. By default, aot is set to true.

Q.53. What is the purpose of metadata json files?

Solution: The metadata.json file can be treated as a diagram of the overall structure of a decorator's metadata, represented as an abstract syntax tree(AST). During the analysis phase, the AOT collector scans the metadata recorded in the Angular decorators and outputs metadata information in .metadata.json files, one per .d.ts file.

Q.54. How do you describe various dependencies in angular applications?

Solution: The dependencies section of package.json within an angular application can be divided as follows:

i)  Angular packages: Angular core and optional modules; their package names begin @angular/.

ii) Support packages: Third-party libraries that must be present for Angular apps to run.

iii) Polyfill packages: Polyfills plug gaps in a browser's JavaScript implementation.

Q.55. What are the class decorators in Angular?

Solution: A class decorator is a decorator that appears immediately before a class definition, which declares the class to be of the given type, and provides metadata suitable to the type.

Q.56. What happens if I import the same module twice?

Solution: If multiple modules import the same module then angular evaluate it only once (When it encounters the module for the first time). It follows this condition even if the module appears at any level in a hierarchy of imported NgModules.

Q.57. What are the ways to trigger change detection in Angular?

Solution: You can inject either ApplicationRef or NgZone, or ChangeDetectorRef into your component and apply the below specific methods to trigger change detection in Angular. i.e, There are 3 possible ways,

  1. ApplicationRef.tick(): Invoke this method to explicitly process change detection and its side effects. It checks the full component tree.
  2. It evaluates the callback function inside the Angular zone.
  3. ChangeDetectorRef.detectChanges(): It detects only the components and their children.

Q.58. What are the security principles in angular?

Solution: Below is the list of security principles in angular,

You should avoid direct use of the DOM APIs.

  1. You should enable Content Security Policy (CSP) and configure your web server to return appropriate CSP HTTP headers.
  2. You should Use the offline template compiler.
  3. You should use Server Side XSS protection.
  4. You should use DOM Sanitizer.
  5. You should prevent CSRF or XSRF attacks.

Q.59. What are the security principles in angular?

Solution: Below is the list of security principles in angular,

  1. You should avoid direct use of the DOM APIs.
  2. You should enable Content Security Policy (CSP) and configure your web server to return appropriate CSP HTTP headers.
  3. You should Use the offline template compiler.
  4. You should use Server Side XSS protection.
  5. You should use DOM Sanitizer.
  6. You should prevent CSRF or XSRF attacks.

Q.60. What is Schematics CLI?

Solution: Schematics comes with its own command-line tool known as Schematics CLI. It is used to install the schematics executable, which you can use to create a new schematics collection with an initial named schematic. The collection folder is a workspace for schematics. You can also use the schematics command to add a new schematic to an existing collection or extend an existing schematic.

Q.61. What are the best practices for security in angular?

Solution: Below are the best practices of security in angular,

Use the latest Angular library releases

Don't modify your copy of the Angular

Avoid Angular APIs marked in the documentation as “Security Risk.”

Q.62. What are the various security contexts in Angular?

Solution: Angular defines the following security contexts for sanitization,

  • HTML: It is used when interpreting a value as HTML such as binding to innerHTML.
  • Style: It is used when binding CSS into the style property.
  • URL: It is used for URL properties such as <a href>.
  • Resource URL: It is a URL that will be loaded and executed as code such as <script src>.

Q.63. What is the difference between AngularJS and Angular?

Solution: The difference between AngularJS and Angular: AngularJS is the first version of the Angular framework, also known as Angular 1.x. AngularJS uses JavaScript to build web applications, whereas Angular 2+ uses TypeScript. AngularJS also has a different syntax and architecture than Angular.

Q.64. What is TypeScript?

Solution: TypeScript is a superset of JavaScript that adds optional static typing and other features to JavaScript. TypeScript is used by Angular to build robust and scalable web applications.

Q.65. What is the difference between ngIf and ngSwitch directives in Angular?

Solution: ngIf is used to conditionally render an element based on a Boolean expression, whereas ngSwitch is used to conditionally render an element based on a value. ngSwitch is useful when there are multiple possible values that need to be checked.

Q.66. What is the difference between ViewChild and ContentChild in Angular?

Solution: ViewChild is used to get a reference to a child component or element in the parent component's template, whereas ContentChild is used to get a reference to a child component or element in the parent component's content projection.

Q.67. What is Angular Universal?

Solution: Angular Universal is a server-side rendering (SSR) solution for Angular applications. It allows the application to be rendered on the server and delivered to the client as HTML, which improves the application's performance and SEO.

Q.68. What is the difference between ngOnChanges and ngOnInit in Angular?

Solution: ngOnChanges is a lifecycle hook in Angular that is called when the input properties of a component change, whereas ngOnInit is called when the component is initialized. ngOnInit is called only once, while ngOnChanges can be called multiple times.

Q.69. What is Angular Ivy?

Solution: Angular Ivy is the new rendering engine introduced in Angular version 9. Ivy improves the performance and size of Angular applications, simplifies the development process, and enables new features.

Q.70. What is the difference between ViewEncapsulation and Shadow DOM in Angular?

Solution: ViewEncapsulation is a way to control how styles are applied to the component's view. Shadow DOM is a browser feature that allows developers to encapsulate the styles and behavior of a component. ViewEncapsulation is a more flexible and widely supported approach to encapsulation.

Q.71. What is a route guard in Angular?

Solution: A route guard is a way to control access to a route in Angular. Route guards can be used to prevent unauthorized access, redirect the user to a login page, or perform other actions before allowing access to the route.

Q.72. What is Angular Material?

Solution: Angular Material is a UI component library for Angular applications. It provides a set of pre-built UI components that follow Google's Material Design guidelines. Angular Material makes it easy to create responsive, accessible, and mobile-friendly applications.

Q.73. What is the purpose of the NgModule decorator in Angular?

Solution: The NgModule decorator is used to define a module in Angular. The decorator specifies the metadata for the module, such as the imports, declarations, providers, and exports. The NgModule decorator is used to organize the application into reusable and cohesive units.

Q.74. What is dependency injection in Angular?

Solution: Dependency injection (DI) is a technique used in Angular to provide instances of dependencies to a class. DI simplifies the management of dependencies and improves the testability and flexibility of the application.

Q.75. What is the difference between HttpClient and Http in Angular?

Solution: HttpClient is a newer and more powerful HTTP client introduced in Angular 4.3. Http is the older HTTP client, which is still supported but not recommended. HttpClient is easier to use and provides more features, such as interceptors, progress events, and support for JSONP.

Q.76. What is the difference between HttpClient and Http in Angular?

Solution: HttpClient is a newer and more powerful HTTP client introduced in Angular 4.3. Http is the older HTTP client, which is still supported but not recommended. HttpClient is easier to use and provides more features, such as interceptors, progress events, and support for JSONP.

Q.77. What is the purpose of the ng-container element in Angular?

Solution: The ng-container element is a non-rendering element that can be used to group elements and apply directives to them. The ng-container element is useful when you want to apply a structural directive, such as ngIf or ngFor, to multiple elements without creating a wrapper element.

Q.78. What is an Angular guard?

Solution: An Angular guard is a class that controls access to a route based on certain conditions. Guards can be used to check if the user is authenticated, has the necessary permissions, or is authorized to access the route.

Q.79. What is the difference between the async pipe and subscribe method in Angular?

Solution: The async pipe is a built-in Angular pipe that subscribes to an observable and updates the view automatically when new data arrives. The subscribe method is used to manually subscribe to an observable and receive notifications when new data arrives. The async pipe is more convenient for displaying asynchronous data in the template, while the subscribe method provides more control over the subscription and allows you to perform side effects.

Q.80. How do you share data between components in Angular?

Solution: There are several ways to share data between components in Angular, including using services, input, and output properties, and the Angular router. Services are the recommended way to share data between components that are not directly related, while input and output properties are used to share data between parent and child components. The Angular router can be used to pass data between components as route parameters or query parameters.

Q.81. What is a resolver in Angular?

Solution: A resolver is a service that is used to fetch data before the route is activated in Angular. Resolvers can be used to ensure that data is available before the component is displayed, and can be used to prevent flicker or empty pages caused by slow network requests.

Q.82. What is a provider in Angular?

Solution: A provider is a recipe for creating an instance of a service or other dependency. Providers can be registered at the component, module, or application level, and are used by Angular's dependency injection system to inject instances of dependencies into components and other parts of the application.

Q.83. What is the difference between a service and a component in Angular?

Solution: A service is a class in Angular that provides functionality that can be shared across multiple components. Services are typically used to encapsulate business logic or data access functionality and can be injected into components that need them. Components, on the other hand, are responsible for the presentation layer of the application and are typically used to create reusable UI components.

Q.84. What is the difference between an ElementRef and a Renderer2 in Angular?

Solution: An ElementRef is a reference to a DOM element in Angular, while a Renderer2 is a service that provides a way to manipulate the DOM in a safe and efficient way. Using an ElementRef directly to modify the DOM can be unsafe, so Renderer2 is used to abstract away the underlying DOM manipulation and provide a safer and more efficient way to manipulate the DOM.

Q.85. What is the difference between a template-driven form and a reactive form in Angular?

Solution: Template-driven forms are a feature in Angular that allows you to create forms using directives in the template. Reactive forms, on the other hand, are a feature that allows you to create forms using reactive programming techniques. Template-driven forms are simpler to use and are more suitable for simple forms, while reactive forms provide more control and flexibility and are more suitable for complex forms.

Q.86. What is an Angular service worker?

Solution: An Angular service worker is a feature in Angular that provides offline support and improves the performance of web applications by caching resources and serving them from the cache when the network is unavailable. The service worker runs in the background and can be used to provide a seamless offline experience for the user.

Q.87. What is the difference between a template and a view in Angular?

Solution: A template is the HTML markup that defines the structure and layout of a component in Angular. The template defines the HTML elements and bindings that are used to render the component. A view, on the other hand, is the rendered output of a component, which includes the template, any data bindings, and any other DOM elements that are added or removed during runtime.

Q.88. What is the Angular change detection mechanism?

Solution: The Angular change detection mechanism is the process by which Angular updates the view when the application state changes. Angular uses a tree of change detectors to track changes to the application state and updates the view when changes are detected. Change detection can be triggered manually, or can be triggered automatically by Angular when events occur, such as user input or HTTP requests.

Q.89. What is the difference between a service and a component in Angular?

Solution: A service in Angular is a class that provides functionality to other parts of the application, while a component is a class that represents a UI element in the application. Services are used to provide shared functionality, such as data access, logging, or authentication, while components are used to define the structure and layout of the application's UI.

Q.90. What is an Angular template reference variable?

Solution: A template reference variable in Angular is a variable that is used to reference a DOM element or Angular component in a template. Template reference variables are typically defined using the # syntax, and can be used to access properties or methods of the referenced element or component.

Q.91. What is a ViewChild decorator in Angular?

Solution: The ViewChild decorator in Angular is used to get a reference to a child component or element in the parent component's template. The decorator is typically used to access a child component's properties or methods from the parent component.

Q.92. What is the difference between a template-driven form and a reactive form in Angular?

Solution: A template-driven form in Angular is a form that is defined in the template using directives such as ngModel and ngForm. Template-driven forms are typically easier to implement, but provide less control and flexibility than reactive forms.

Q.93. What is an Angular module?

Solution: An Angular module is a container for related components, directives, pipes, and services. Modules help to organize an application into smaller, more manageable pieces, and provide a way to share code and functionality across the application.

Q.94. What is NgZone in Angular?

Solution: NgZone is a service in Angular that provides a way to execute code outside of the Angular zone. The Angular zone is a concept that is used to track changes to the application state, and NgZone provides a way to run code that should not trigger change detection or other Angular lifecycle hooks.

Q.95. What is the difference between ngOnInit and ngAfterViewInit in Angular?

Solution: In Angular, ngOnInit, and ngAfterViewInit are lifecycle hooks that are used to perform tasks during different stages of a component's lifecycle. ngOnInit is called after the component is constructed and all its properties have been initialized, while ngAfterViewInit is called after the component's view has been initialized and all its child views have been rendered. These hooks can be used to perform tasks such as initializing data, interacting with the DOM, or setting up event listeners, and can help to ensure that your application runs smoothly and efficiently.

Q.96. What is the purpose of the HostListener decorator in Angular?

Solution: In Angular, the HostListener decorator is used to register event listeners on the host element of a component. This allows you to listen for events such as mouse clicks, key presses, or touch events, and perform actions in response to them. The HostListener decorator can be applied to a method within a component, and takes a string parameter that specifies the name of the event to listen for. When the event is triggered on the host element, the method is called and can perform any necessary actions.

Q.97. What is the purpose of the ng-template directive in Angular?

Solution: The ng-template directive is used to define a template that can be reused across multiple components. Templates can be used to define reusable UI components or to define the logic that is shared across multiple views.

Q.98. What is the purpose of the ActivatedRoute service in Angular?

Solution: In Angular, the ActivatedRoute service is used to obtain information about the currently activated route. This service provides access to the route parameters, which are used to pass data between different components, as well as query parameters, which are used to modify the behavior of the current route. By using the ActivatedRoute service, you can easily obtain and manipulate route data within your Angular application, allowing you to create dynamic and interactive user interfaces.

Q.99. What is the purpose of the async/await syntax in Angular?

Solution: In JavaScript, the async/await syntax is a way to write asynchronous code in a synchronous style. This syntax allows you to write asynchronous code using try/catch blocks and return statements, making it easier to read and reason about complex code. The async/await syntax also ensures that errors are properly handled, making it a more reliable way to write asynchronous code.

Q.100. What is the purpose of the ngClass directive in Angular?

Solution: The ngClass directive is used to conditionally apply CSS classes to elements in the template based on a boolean expression. This can be useful for styling elements based on the state of the application.


In conclusion, this comprehensive list of the top 100 Angular interview questions serves as a valuable resource for anyone preparing for an Angular JS interview or looking to test their knowledge of the framework. By familiarizing yourself with these interview questions on Angular, you will not only increase your chances of success in the interview process, but also gain a deeper understanding of Angular's key concepts and best practices. Regardless of your experience level, reviewing these Angular JS interview questions will help you stay up-to-date with the latest trends and developments in the ever-evolving world of web development. Good luck, and may your Angular interviews be a success!

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