100+ Angular Developer Interview Questions and Answers

Passing data between parent and child components is component interaction in Angular.

• Use @Input decorator to pass data from parent to child component

• Use @Output decorator and EventEmitter to pass data from child to parent component

• Use services to share data between components

• Use ViewChild to access child component's properties and methods from parent component

Life cycle hooks are methods that get called at specific stages of a component's life cycle.

• ngOnInit() - called after the component is initialized

• ngOnChanges() - called when the component's input properties change

• ngOnDestroy() - called just before the component is destroyed

• Used to perform specific actions at different stages of a component's life cycle

• Yes, I have worked on them in my project

The latest version of TypeScript used in my project has several new features.

• Optional Chaining and Nullish Coalescing

• Improved performance with faster compilation times

• Support for private fields and methods

• Higher order type inference from generic constructors

• Support for ECMAScript private fields

• Improved support for tuples

• Smaller bundle sizes with tree shaking

Improving performance of an application can be achieved through various ways.

• Optimizing code by reducing unnecessary calculations and improving algorithms

• Caching data to reduce database queries and network requests

• Lazy loading modules and components to improve initial load time

• Minifying and compressing files to reduce file size and improve loading speed

• Using server-side rendering to improve initial rendering time

• Implementing code splitting to load only required code

• Optimizing...read more

Lazy loading is a technique to load modules on demand instead of loading everything at once.

• Lazy loading improves the initial load time of the application.

• It splits the application into smaller chunks that can be loaded when needed.

• In Angular, lazy loading is achieved by configuring the routes with loadChildren property.

• Syntax for routing path with lazy loading: { path: 'lazy', loadChildren: () => import('./lazy/lazy.module').then(m => m.LazyModule) }

Angular has four types of data bindings: Interpolation, Property binding, Event binding, and Two-way binding.

• Interpolation: {{ expression }}

• Property binding: [property]="expression"

• Event binding: (event)="expression"

• Two-way binding: [(ngModel)]="expression"

Observables are streams of data that can be observed, while Subjects are both observers and observables.

• Observables are unicast, meaning each subscribed observer receives its own stream of data.

• Subjects are multicast, meaning they can have multiple observers and share the same stream of data.

• Observables are cold, meaning they start emitting data only when subscribed to.

• Subjects are hot, meaning they start emitting data immediately upon creation.

• Observables can be transformed ...read more

Answers to common questions asked in an Angular Developer interview.

• var, const, and let are used to declare variables in JavaScript

• var has function scope, while let and const have block scope

• const is used to declare variables that cannot be reassigned

• let is used to declare variables that can be reassigned

• ES6 introduced new features like arrow functions, template literals, and destructuring

• Closure is a function that has access to variables in its outer scope, even after the ou...read more

Route guards are used to control access to routes in Angular applications.

• Route guards are used to protect routes from unauthorized access.

• They can be used to check if a user is authenticated or has certain permissions before allowing access to a route.

• There are three types of route guards in Angular: CanActivate, CanActivateChild, and CanLoad.

• CanActivate is used to determine if a route can be activated.

• CanActivateChild is used to determine if a child route can be activated.

• C...read more

Answering questions related to Angular development

• Dependency injection is a way to provide dependencies to a class

• forRoot is used to configure services at the root level

• forChild is used to configure services at the child level

• Reusable components can be created by breaking down complex components into smaller ones

• Services can be injected using constructor injection or property injection

To call REST APIs in Angular, use the HttpClient module and its methods like get(), post(), put(), delete().

• Import the HttpClientModule in your Angular module

• Inject the HttpClient service in your component or service

• Use the HttpClient methods to make HTTP requests to the REST APIs

• Handle the response using observables and subscribe to them

• Example: httpClient.get('https://api.example.com/data')

• Example: httpClient.post('https://api.example.com/data', postData)

Strict operator (!) is used to check if a value is truthy or falsy. Rest operator (...) is used to collect multiple arguments into an array.

• Strict operator (!) checks if a value is truthy or falsy, for example: if (!value) { // do something }

• Rest operator (...) collects multiple arguments into an array, for example: function sum(...args) { return args.reduce((acc, val) => acc + val, 0); }

Lazy loading, AOT, GIT compilation, Promises, Observables, and differences between Angular and AngularJS.

• Lazy loading is a technique to load modules on demand.

• AOT (Ahead of Time) compilation compiles templates during build time.

• GIT compilation is a process of compiling TypeScript code to JavaScript.

• Promises are used for asynchronous programming and represent a single value that may be available now, in the future, or never.

• Observables are used for asynchronous programming and...read more

Overview of key web development concepts including HTML semantics, CSS Flexbox, Angular features, and JavaScript functions.

• D/B Semantics: Refers to the use of meaningful HTML elements (e.g., <header>, <footer>) to enhance accessibility and SEO.

• CSS Flexbox: A layout model that allows responsive design by aligning items in rows or columns. Example: 'display: flex;'

• Finding HTML Version: Check the DOCTYPE declaration at the top of an HTML document (e.g., <!DOCTYPE html> for HTML5...read more

NGRX can handle large amounts of data by using lazy loading, pagination, and memoization techniques.

• Implement lazy loading to only load data when needed

• Use pagination to limit the amount of data loaded at once

• Utilize memoization to cache results and avoid unnecessary computations

Routing is the process of navigating between different components or pages in an Angular application.

• Routing is used to create single-page applications (SPAs) where the content is dynamically loaded without refreshing the entire page.

• In Angular, routing is achieved using the RouterModule and the RouterLink directives.

• The RouterModule is imported from the @angular/router package and added to the imports array of the app module.

• Routes are defined as an array of objects, where e...read more

Lazy loading is a technique in Angular that loads modules or components on-demand, improving performance.

• Lazy loading helps reduce initial load time by loading modules or components only when needed

• It improves performance by splitting the application into smaller chunks

• Syntax: import() function is used to dynamically load modules or components

Data can be shared between components using services, input/output bindings, and state management libraries.

• Create a service to hold the data and inject it into the components that need it

• Use input/output bindings to pass data between parent and child components

• Use state management libraries like NgRx or Redux to manage shared data across components

• Use a shared module to import and export components that need to share data

• Use a shared data store like Firebase or GraphQL to st...read more

Observable is for handling multiple values over time, while Promise is for handling a single value.

• Observable can emit multiple values over time, while Promise can only emit a single value.

• Observable can be cancelled, while Promise cannot be cancelled.

• Observable provides operators for transforming and combining data, while Promise does not have such operators.

• Observable is lazy, meaning it won't start emitting values until someone subscribes to it, while Promise starts execut...read more

A custom pipe in Angular is a feature that allows you to transform data in templates.

• Custom pipes are created by implementing the PipeTransform interface in a class.

• The class must have a transform method that takes input data and optional parameters.

• Custom pipes are then declared in the module's declarations array and can be used in templates.

• Example: Creating a custom pipe to format dates in a specific way.

Authentication verifies the identity of a user, while authorization determines what a user can access.

• Authentication confirms the user's identity through credentials like username and password.

• Authorization controls the user's access to resources or features based on their authenticated identity.

• Example: Logging into a website (authentication) and then being able to view/edit specific pages based on user roles (authorization).

Promises are used for asynchronous operations that return a single value, while observables are used for asynchronous operations that return multiple values over time.

• Promises return a single value and are not cancellable.

• Observables return multiple values over time and can be cancelled.

• Promises are eager and start executing immediately upon creation.

• Observables are lazy and do not execute until subscribed to.

• Promises can only be resolved or rejected once.

• Observables can emit...read more

Data binding is the automatic synchronization of data between the model and view. Angular uses two-way data binding.

• Data binding is the process of connecting the model and view in an application.

• It allows changes in the model to automatically update the view, and vice versa.

• Angular uses two-way data binding, which means changes in the model or view are reflected in both directions.

• Example: If a user updates a form input field, the corresponding model property is updated and a...read more

ES6 features are modern JavaScript syntax enhancements introduced in ECMAScript 2015.

• Arrow functions for concise syntax: const add = (a, b) => a + b;

• Let and const for block-scoped variables: let x = 5; const y = 10;

• Template literals for string interpolation: const name = 'Alice'; console.log(`Hello, ${name}!`);

• Classes for object-oriented programming: class Person { constructor(name) { this.name = name; } }

• Destructuring for easy assignment: const { a, b } = { a: 1, b: 2 };

• Spre...read more

The @Input() and @Output() are decorators in Angular used for communication between parent and child components.

• The @Input() decorator is used to pass data from a parent component to a child component.

• The @Output() decorator is used to emit events from a child component to a parent component.

• The @Input() property is bound to a value in the parent component template using property binding.

• The @Output() property is bound to an event in the child component template using event b...read more

Use observables and combineLatest operator to fetch data from multiple services in a component

• Create observables for each service call

• Use combineLatest operator to combine the observables and fetch data from all services at once

• Subscribe to the combined observable to get the data

Angular performance optimization involves using best practices to improve the speed and efficiency of Angular applications. ngOnChanges is a lifecycle hook in Angular that is called when a data-bound input property value changes.

• Use trackBy function in ngFor to improve performance when rendering lists

• Lazy load modules to reduce initial load time

• Minimize the use of two-way data binding to avoid unnecessary change detection cycles

• Optimize network requests by using HTTP intercep...read more