200+ Angular Frontend Developer Interview Questions and Answers

Understanding JavaScript concepts like parameters, closures, and variable declarations is crucial for effective coding.

• Parameters are variables listed as part of a function's definition, while arguments are the actual values passed to the function.

• Example: function add(a, b) { return a + b; } - 'a' and 'b' are parameters; add(2, 3) - '2' and '3' are arguments.

• Closures are functions that remember their lexical scope even when the function is executed outside that scope.

• Example...read more

To call an API in Angular, use HttpClient module to make HTTP requests.

• Import HttpClientModule in app.module.ts

• Inject HttpClient in the component/service where API call needs to be made

• Use HttpClient methods like get(), post(), put(), delete() to make API calls

• Subscribe to the Observable returned by HttpClient methods to handle the response

Use JavaScript to find repeating alphabets in an array of strings.

• Loop through each string in the array

• For each string, loop through each character and check if it is repeated

• Store the repeating alphabets in a separate array

There are multiple ways to communicate in Angular components, including Input, Output, ViewChild, and Services.

• Input - parent component can pass data to child component using @Input decorator

• Output - child component can emit events to parent component using @Output decorator

• ViewChild - parent component can access child component using @ViewChild decorator

• Services - components can communicate through shared services

Optimize Angular app performance by using lazy loading, change detection strategies, and efficient data handling.

• Use Lazy Loading: Load feature modules only when needed to reduce initial load time. Example: Use 'loadChildren' in routing.

• Implement Change Detection Strategies: Use OnPush strategy to minimize checks. This can improve performance by reducing unnecessary checks.

• Optimize Template Expressions: Avoid complex expressions in templates. Pre-compute values in the compone...read more

Responsive web design ensures optimal viewing across devices by adapting layout and content to different screen sizes.

• Use flexible grid layouts that adjust based on screen size, e.g., CSS Grid or Flexbox.

• Implement media queries to apply different styles for various screen widths, e.g., @media (max-width: 600px) { ... }.

• Utilize responsive images with the 'srcset' attribute to serve different image sizes based on device resolution.

• Adopt a mobile-first approach by designing for ...read more

TypeScript is a superset of JavaScript that adds static typing and other features for better development experience.

• TypeScript is statically typed, while JavaScript is dynamically typed. Example: In TS, you can define a variable as 'let num: number = 5;'.

• TypeScript supports interfaces and enums, which help in defining contracts and enumerations. Example: 'interface User { name: string; age: number; }'.

• TypeScript provides better tooling and IDE support, including autocompletio...read more

Data binding is a technique that connects the UI to the data model, enabling automatic synchronization between them.

• Types of data binding: One-way binding (e.g., displaying data) and two-way binding (e.g., form inputs).

• Example of one-way binding: Using interpolation to display a variable in the template: {{ variableName }}.

• Example of two-way binding: Using ngModel in forms to bind input values to a component property.

• Data binding enhances user experience by ensuring that the ...read more

Answers to questions related to Angular frontend development

• To create a custom pipe, use the @Pipe decorator and implement the PipeTransform interface

• Directives in Angular are used to manipulate the DOM and add behavior to elements

• Binding in Angular is used to connect the component class with the template

• Examples of binding include property binding, event binding, and two-way binding

JavaScript is single-threaded due to its event loop, yet it handles asynchronous operations using callbacks, promises, and async/await.

• JavaScript runs on a single thread, meaning it can execute one command at a time.

• Asynchronous operations allow JavaScript to perform tasks like fetching data without blocking the main thread.

• The event loop manages asynchronous callbacks, enabling JavaScript to handle events and I/O operations efficiently.

• Example: Using 'setTimeout' allows a fu...read more

A pipe in Angular is used to transform data before displaying it in the template.

• Pipes are used in templates to format data before displaying it to the user

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

• Custom pipes can also be created by implementing the PipeTransform interface

• Pipes can be chained together to perform multiple transformations on the data

Create a reactive form in Angular to save data in API with validation

• Create a reactive form using FormBuilder in Angular

• Add form controls with proper validation rules using Validators

• Handle form submission and send data to API using HttpClient

• Implement error handling for API requests

• Display success or error messages to the user

Handling large-scale API responses in Angular involves efficient data management, pagination, and lazy loading techniques.

• Pagination: Implement pagination to load data in chunks, reducing the initial load time. For example, use Angular Material's paginator component.

• Lazy Loading: Use lazy loading to load modules only when needed, which can help in managing large datasets efficiently.

• Data Caching: Implement caching strategies to store previously fetched data, minimizing API ca...read more

Angular is a JavaScript framework for building web applications. It uses TypeScript and follows the MVC architecture.

• Angular has a modular architecture with components, services, and modules.

• The folder structure includes app, assets, environments, and node_modules folders.

• The app folder contains the main application code, including components, services, and modules.

• The assets folder contains static files like images and fonts.

• The environments folder contains environment-speci...read more

Arrow functions provide a concise syntax and lexical scoping of 'this', differing from traditional function expressions.

• Syntax: Arrow functions use a shorter syntax, e.g., const add = (a, b) => a + b; vs function add(a, b) { return a + b; }.

• Lexical 'this': Arrow functions do not have their own 'this' context; they inherit 'this' from the parent scope, unlike normal functions.

• Implicit return: If the function body consists of a single expression, arrow functions can return it i...read more

Standalone components in Angular 14 allow for independent component usage without needing a module.

• Standalone components can be declared using the `@Component` decorator with the `standalone: true` property.

• They can be used directly in templates without being part of an NgModule.

• Example: `@Component({ selector: 'app-standalone', standalone: true, template: '<h1>Hello</h1>' })`.

• Standalone components can import other standalone components or modules directly.

• They simplify the c...read more

Calling detectChanges() triggers Angular's change detection for the component, updating the view with any changes in data.

• detectChanges() checks the component and its children for changes in data bindings.

• It updates the view immediately, reflecting any changes in the component's state.

• Example: If a property in the component changes, calling detectChanges() will update the UI without waiting for the next change detection cycle.

• Useful in scenarios where Angular's automatic chan...read more

The map to use for auto complete is the Trie data structure.

• Trie is a tree-like data structure that efficiently stores and retrieves strings.

• It is commonly used for auto complete functionality as it allows for fast prefix matching.

• Each node in the Trie represents a character, and the edges represent the next possible characters.

• By traversing the Trie, all possible completions for a given prefix can be found.

• Example: Searching for 'app' in a Trie containing 'apple', 'applicati...read more

Optimize change detection in Angular for heavy components using strategies like OnPush, manual detection, and trackBy.

• Use ChangeDetectionStrategy.OnPush to limit checks to input-bound properties.

• Implement manual change detection using ChangeDetectorRef.detectChanges() when necessary.

• Utilize trackBy in ngFor to optimize rendering of lists, reducing unnecessary checks.

• Leverage Observables and async pipe to automatically manage subscriptions and change detection.

• Consider using t...read more

Use JavaScript to remove duplicate elements from an array of strings.

• Create a new Set from the array to automatically remove duplicates

• Convert the Set back to an array to get the final result

Using a shared service or event emitter to facilitate communication between non-relatable components.

• Create a shared service with methods to send and receive data between components

• Use event emitters to emit events and pass data between components

• Utilize RxJS subjects to create an observable data stream for communication

Angular is a JavaScript framework for building web applications. SPA came in picture for better user experience.

• Angular is a client-side framework developed by Google.

• It allows developers to build dynamic, single-page web applications.

• SPA (Single Page Application) came in picture to provide a better user experience by reducing page reloads and improving performance.

• SPA loads all the necessary resources (HTML, CSS, JS) at once and dynamically updates the content as the user in...read more

Fetch data from an API and display it in Angular, using a custom pipe to format IDs.

• Use HttpClient to make API calls: `this.http.get(apiUrl).subscribe(data => this.data = data);`

• Create a custom pipe using Angular CLI: `ng generate pipe idFormatter`.

• In the pipe, implement `transform(value: number): string` to convert ID to 1**8 format.

• Use the pipe in the template: `{{ id | idFormatter }}` to display formatted IDs.

Form validations in Angular are built using Angular forms and validators.

• Use Angular forms to create form controls and group them together

• Apply built-in validators like required, minlength, maxlength, pattern, etc.

• Create custom validators for complex validation requirements

• Display error messages based on validation status

• Use reactive forms for more control and flexibility

Reactive forms are more flexible and allow for complex form validation and handling, while template driven forms are simpler and rely on directives in the template.

• Reactive forms are defined programmatically in the component class using form controls, form groups, and form arrays.

• Template driven forms are defined in the HTML template using ngModel directive and template variables.

• Reactive forms offer more control over form validation and submission logic.

• Template driven forms...read more

Centering a div in SCSS can be achieved using various techniques like flexbox, grid, or margin auto.

• Use Flexbox: Set display: flex; and justify-content: center; align-items: center; on the parent.

• Example: .parent { display: flex; justify-content: center; align-items: center; } .child { width: 50%; }

• Use Grid: Set display: grid; and place the child in the center.

• Example: .parent { display: grid; place-items: center; } .child { width: 50%; }

• Use Margin Auto: Set width on the chil...read more

Services are used to share data and functionality across components in Angular applications.

• Services are singleton objects that can be injected into components, directives, and other services.

• They are used to share data and functionality across components.

• Services can be used to make HTTP requests, handle authentication, and perform other tasks.

• They can also be used to encapsulate complex business logic and keep components lean.

• Services can be provided at the component level ...read more