100+ Angular Frontend Developer Interview Questions and Answers

Pipes in Angular are used to transform data before displaying it in the view.

• Pipes are used in Angular templates to format data before displaying it.

• There are built-in pipes like DatePipe, UpperCasePipe, LowerCasePipe, etc.

• Custom pipes can also be created for specific formatting needs.

• Pipes can be chained together for more complex transformations.

Directives are markers on a DOM element that tell AngularJS to attach a specified behavior to that DOM element.

• Directives are used to create reusable components.

• They can be used to manipulate the DOM.

• They can be used to add behavior to an existing DOM element.

• They can be used to create custom attributes.

• Examples include ng-repeat, ng-show, and ng-hide.

Deep copy creates a new copy of an object with all nested objects also copied, while shallow copy creates a new object with references to the original nested objects.

• Deep copy creates a new object and recursively copies all nested objects, resulting in a completely independent copy.

• Shallow copy creates a new object but only copies the references to nested objects, so changes in nested objects reflect in both the original and copied objects.

• Example: deep copy - JSON.parse(JSON...read more

null is an intentional absence of any value, undefined means a variable has been declared but not assigned a value, and empty values are variables that have been assigned a value of empty string, empty array, or empty object.

• null is used to represent the intentional absence of any value

• undefined means a variable has been declared but not assigned a value

• Empty values can be empty string (''), empty array ([]), or empty object ({})

ReplaySubject is a type of Subject in RxJS that records multiple values and replays them to new subscribers.

• ReplaySubject is a type of Subject in RxJS

• It records multiple values and replays them to new subscribers

• It has a buffer size that determines how many values to replay

Lazy loading is a technique used to load only the necessary resources for a specific part of a web application when it is needed.

• Lazy loading can be achieved in Angular by using the loadChildren property in the route configuration.

• This property allows you to specify a separate module that will be loaded only when the route is activated.

• Lazy loading helps improve the initial loading time of the application by loading modules on demand rather than all at once.

Decorators are functions that modify classes, methods, or properties at design time.

• Decorators are used in Angular to add metadata to classes, methods, and properties.

• They are denoted by the @ symbol and placed immediately before the item being decorated.

• Examples include @Component, @Injectable, and @Input.

• Decorators can be used to provide additional functionality or configuration to Angular components.

Routing in Angular is the process of navigating between different components and views based on the URL.

• Routing is defined in the app-routing.module.ts file

• Routes are defined using the RouterModule.forRoot() method

• Each route maps a URL path to a component

• RouterLink directive is used to navigate between routes in HTML

• Router.navigate() method is used to navigate programmatically

• Child routes can be defined for nested components

Time queue in API refers to managing requests in a sequential order.

• Time queue ensures that API requests are processed in the order they are received.

• It helps in preventing overload on the server by limiting the number of concurrent requests.

• Examples include using promises or async/await in JavaScript to handle API calls sequentially.

Code to check if a string is a palindrome or not

• Create a function that takes a string as input

• Remove all non-alphanumeric characters and convert to lowercase

• Compare the string with its reverse to check if it's a palindrome

Angular is the newer version of AngularJS with improved features and performance.

• Angular is a complete rewrite of AngularJS.

• Angular uses TypeScript while AngularJS uses JavaScript.

• Angular has a more component-based architecture.

• Angular has better performance and improved dependency injection compared to AngularJS.

• Angular has a more streamlined and simplified syntax compared to AngularJS.

Use JavaScript to find the longest word in a string.

• Split the string into an array of words using split() method.

• Iterate through the array and compare the length of each word to find the longest one.

• Return the longest word found.

Reactive forms in Angular allow for creating and managing forms in a reactive way.

• Import ReactiveFormsModule in app.module.ts

• Create form controls using FormBuilder in component

• Bind form controls to HTML elements using formGroup and formControlName directives

• Handle form submission and validation using formGroup and formControl directives

Yes, I am able to task solving by breaking down complex problems into smaller tasks and finding solutions.

• I have experience in breaking down complex requirements into manageable tasks

• I am skilled in problem-solving techniques and can find solutions efficiently

• I have successfully completed tasks in previous projects by following a systematic approach

API stands for Application Programming Interface. It defines the methods and data formats that applications can use to communicate with each other.

• API is a set of rules and protocols that allow different software applications to communicate with each other.

• It specifies how software components should interact, including what data can be accessed and how it should be accessed.

• APIs can be used to access data from a web server, interact with a database, or integrate with third-pa...read more

Use JavaScript to capitalize the first letter of each word in a sentence

• Split the sentence into an array of words

• Loop through each word and capitalize the first letter using charAt() and toUpperCase()

• Join the words back together into a sentence

Redux is a predictable state container for JavaScript apps, and RxJS is a library for reactive programming using Observables.

• Redux is a state management tool commonly used with React to manage application state in a predictable way.

• RxJS is a library for reactive programming that allows you to work with asynchronous data streams using Observables.

• Redux helps in managing the state of the application in a single immutable state tree.

• RxJS allows you to work with asynchronous data...read more

RxJS is a library for reactive programming using Observables, allowing for easier handling of asynchronous data streams.

• RxJS stands for Reactive Extensions for JavaScript

• It provides a way to work with asynchronous data streams

• Operators like map, filter, and mergeMap can be used to manipulate and combine streams

• Subscriptions are used to listen for values emitted by Observables

An arrow function is a concise way to write a function in JavaScript.

• Uses the '=>' syntax

• Does not have its own 'this' keyword

• Cannot be used as a constructor

• Can be used as a callback function

Services are reusable code that can be shared across components, while components are building blocks of an Angular application.

• Services are used for fetching data from a server, sharing data between components, and encapsulating reusable logic.

• Components are responsible for the UI and user interactions, and can be thought of as custom HTML elements.

• Services are typically singleton instances, while components are instantiated multiple times.

• Components have a template, styles,...read more

Angular app starts by bootstrapping the root module and creating the component tree.

• Angular app starts by loading the main.ts file, which bootstraps the root module of the application.

• The root module then defines the component tree, which represents the structure of the application.

• Angular creates instances of components and injects services as needed to render the application.

• The AppComponent is typically the root component of the application, which is defined in the AppModu...read more

Security in Angular applications is implemented through various mechanisms such as HTTPS, input validation, authentication, authorization, and secure coding practices.

• Use HTTPS to encrypt data transmitted between the client and server.

• Implement input validation to prevent malicious input from users.

• Utilize authentication mechanisms like JWT tokens or OAuth for user identity verification.

• Implement authorization to control access to different parts of the application based on u...read more

Lazy loading in Angular is a technique used to load modules only when they are needed, improving performance by reducing initial load time.

• Lazy loading helps in splitting the application into multiple bundles which are loaded on demand.

• It is achieved by using the loadChildren property in the route configuration.

• Lazy loading is commonly used for optimizing large applications with multiple modules.

• Example: loadChildren: () => import('./lazy-loaded-module').then(m => m.LazyLoade...read more

Pipes in Angular are used to transform data before displaying it in the view.

• Pipes are used to format data in templates.

• They can be used to filter, sort, or transform data.

• Examples include currency, date, and uppercase pipes.

Call and apply are both methods used to invoke a function with a specific 'this' value.

• Call takes arguments as a comma-separated list, while apply takes arguments as an array.

• Call is used when the number of arguments is known, while apply is used when the number of arguments is unknown.

• Call is generally faster than apply.

• Both methods are used to set the 'this' value of a function.

foreach is used to iterate over an array and perform a function on each element, while map creates a new array by applying a function to each element.

• foreach does not return a new array, while map does

• foreach is used for side effects, while map is used for transformation

• Example: forEach - let numbers = [1, 2, 3]; numbers.forEach(num => console.log(num)); // prints 1, 2, 3

• Example: map - let numbers = [1, 2, 3]; let doubled = numbers.map(num => num * 2); // doubled is [2, 4, 6]

Directives in Angular are markers on a DOM element that tell Angular to attach a specified behavior to that DOM element or transform the DOM element and its children.

• Directives are used to create reusable components in Angular.

• There are three types of directives in Angular: Component, Structural, and Attribute directives.

• Examples of directives include ngIf, ngFor, and ngStyle.

Closure is a function that has access to its own scope, as well as the scope of its outer function.

• A closure allows a function to access variables from its outer function even after the outer function has finished executing.

• Closures are commonly used in JavaScript to create private variables and functions.

• Example: function outerFunction() { let outerVar = 'I am outer'; return function innerFunction() { console.log(outerVar); }; }

Sort array without using methods

• Iterate through the array and compare each element with the rest to find the correct position

• Swap elements if necessary to sort the array in ascending order

• Repeat the process until the array is fully sorted

Dependency Injection is a design pattern in which a class receives its dependencies from external sources rather than creating them itself.

• Allows for easier testing by injecting mock dependencies

• Promotes reusability and modularity by decoupling components

• Reduces code duplication by centralizing dependency creation

• Example: Angular uses Dependency Injection to provide services to components

A function to reverse a given string.

• Create an empty string variable to store the reversed string.

• Loop through the original string from the end to the beginning.

• Add each character to the empty string variable.

• Return the reversed string.

SVG is a vector-based graphics format while Canvas is a bitmap-based graphics format.

• SVG uses XML to define graphics and is resolution-independent.

• SVG elements can be styled with CSS and manipulated with JavaScript.

• Canvas is a pixel-based grid where graphics are drawn programmatically.

• Canvas is more suitable for complex animations and real-time rendering.

• Canvas has better performance for rendering large amounts of data.

Angular life cycle refers to the series of events that occur from the creation of a component to its destruction.

• Angular components go through various stages like creation, rendering, updating, and destruction.

• Some key life cycle hooks include ngOnInit, ngOnChanges, ngDoCheck, ngOnDestroy, etc.

• Developers can use these hooks to perform tasks like initializing data, reacting to changes, and cleaning up resources.

Rxjs is a library for reactive programming using observables and subjects.

• Observables are streams of data that can be subscribed to.

• Subjects are both an observable and an observer, allowing for multicasting.

• Rxjs provides operators for manipulating and transforming data streams.

• Reactive programming allows for asynchronous and event-driven programming.

• Example: An observable can be created from an HTTP request and subscribed to for the response data.

Lexical this in JavaScript refers to the value of 'this' inside a function, which is determined by where the function is declared.

• Lexical this allows functions to access the 'this' value of their enclosing scope.

• It is not affected by how or where the function is called, unlike regular functions.

• Arrow functions in JavaScript use lexical this, making it easier to maintain the context of 'this'.

Pipes in Angular are used to transform data in templates.

• Pipes are used to format data before displaying it in the view.

• They can be used to filter, sort, or manipulate data in various ways.

• Examples include currency, date, uppercase, and lowercase pipes.

Angular 17 introduces new features such as improved performance, enhanced tooling, and updated APIs.

• Improved performance with faster rendering and reduced bundle sizes

• Enhanced tooling with better support for debugging and testing

• Updated APIs for more efficient development and easier integration with other libraries

Auth-guard is a feature in Angular that controls access to routes based on user authentication status.

• Auth-guards are used to protect routes in Angular applications by checking if a user is authenticated before allowing access.

• They can be implemented using canActivate interface in Angular.

• Auth-guards can redirect unauthenticated users to a login page or display an error message.

• They are commonly used in applications with restricted access to certain routes or features.

Shallow copy only copies the reference of an object, while deep copy creates a new object with new references.

• Shallow copy creates a new object but references the same nested objects.

• Deep copy creates a new object and recursively copies all nested objects.

• Shallow copy can be achieved using Object.assign or spread operator.

• Deep copy can be achieved using JSON.parse(JSON.stringify(obj)).

Directives in Angular are markers on a DOM element that tell Angular to attach a specified behavior to that DOM element or transform the DOM element and its children.

• Directives are used to extend the functionality of HTML elements.

• There are three types of directives in Angular: Component, Structural, and Attribute directives.

• Examples of directives include ngIf, ngFor, ngStyle, and ngClass.

A linked list is a data structure consisting of nodes where each node points to the next node in the sequence.

• Consists of nodes connected by pointers

• Does not have a fixed size like arrays

• Can be singly linked or doubly linked

• Example: Singly linked list: 1 -> 2 -> 3 -> null

Merge Sort is a divide and conquer algorithm that divides the input array into two halves, sorts them recursively, and then merges them back together in sorted order.

• Divide the input array into two halves

• Sort each half recursively

• Merge the sorted halves back together in sorted order

• Time complexity of O(n log n)

• Example: [38, 27, 43, 3, 9, 82, 10] -> [3, 9, 10, 27, 38, 43, 82]

Pipes in Angular are used to transform data before displaying it in the view.

• Pipes are used to format data in templates.

• They can be used to filter, order, or transform data.

• Examples include currency, date, and uppercase pipes.

RxJS operators are functions used to manipulate and work with streams of data in reactive programming.

• RxJS operators are used to transform, filter, combine, and handle errors in data streams.

• Examples of RxJS operators include map, filter, mergeMap, switchMap, catchError, and debounceTime.

• Operators are used in combination with Observables to create powerful data processing pipelines.

• Understanding and mastering RxJS operators is essential for efficient data handling in Angular ...read more

List is mutable and can be modified, while tuple is immutable and cannot be changed.

• List can be modified by adding, removing, or changing elements.

• Tuple cannot be modified once it is created.

• Example: list = [1, 2, 3], tuple = (1, 2, 3)

Angular interceptors are a way to intercept HTTP requests and responses to perform operations like logging, modifying requests, or handling errors.

• Interceptors can be used to modify outgoing requests or incoming responses.

• They can be used for tasks like adding headers, logging requests, handling errors, or transforming data.

• Interceptors are implemented as services that implement the HttpInterceptor interface.

• Multiple interceptors can be chained together to perform different t...read more

ngClass is used to conditionally apply CSS classes to an element in Angular.

• Use ngClass directive in the template with an object or array of classes and conditions

• Classes are applied when the condition is true, and removed when false

• Example: