30+ Senior Angular Developer Interview Questions and Answers

Dependency Injection in Angular allows for the injection of dependencies into components, services, and other Angular constructs.

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

• @Self decorator specifies that the dependency should be resolved from the current component or directive, rather than looking up the hierarchy.

• @SkipSelf decorator specifies that the dependency should be resolved ...read more

Angular uses HttpClient for making HTTP requests, enabling communication with backend services.

• Import HttpClientModule in your app module: `import { HttpClientModule } from '@angular/common/http';`

• Inject HttpClient in your service or component: `constructor(private http: HttpClient) {}`

• Use HttpClient methods like `get`, `post`, `put`, and `delete` for requests.

• Example of a GET request: `this.http.get('https://api.example.com/data').subscribe(data => console.log(data));`

• Handle...read more

A prime number is a natural number greater than 1 that cannot be formed by multiplying two smaller natural numbers.

• A prime number has exactly two distinct positive divisors: 1 and itself.

• Examples of prime numbers include 2, 3, 5, 7, 11, and 13.

• The number 1 is not considered a prime number.

• The only even prime number is 2; all other even numbers can be divided by 2.

ng-content is for content projection, while ng-template is for defining reusable templates in Angular.

• ng-content allows you to project content into a component from its parent.

• Example: <ng-content></ng-content> in a component template lets parent content be inserted.

• ng-template defines a template that can be instantiated later, often used with structural directives.

• Example: <ng-template #myTemplate>...</ng-template> can be used with *ngIf or *ngFor.

• ng-content is used for tran...read more

Observables are streams of data that can emit multiple values over time, while promises handle a single asynchronous value.

• Observables can emit multiple values, while promises only resolve once.

• Observables are lazy and only execute when subscribed to, whereas promises execute immediately.

• Observables support operators like map, filter, and reduce, enabling powerful data manipulation.

• Example: Observable can be used for handling user input events, while a promise is suitable for...read more

ng-template, ng-content, and ng-container are Angular structural directives used for template rendering and content projection.

• ng-template is used to define a template that can be rendered conditionally or multiple times.

• ng-content is used for content projection, allowing the insertion of content from a parent component into a child component.

• ng-container is a grouping element that doesn't interfere with styles or layout, often used to wrap multiple elements for structural pu...read more

Demonstrating filter and map methods on an array of numbers in JavaScript.

• Use filter to create a new array with numbers greater than a specific value. Example: const filtered = numbers.filter(num => num > 10);

• Use map to transform each number in the array. Example: const squared = numbers.map(num => num * num);

• Combine filter and map to first filter the array and then transform it. Example: const result = numbers.filter(num => num > 10).map(num => num * num);

I have worked on Angular versions 2, 4, 6, 8, 10, and 12.

• Worked on Angular 2, which introduced components, modules, services, and directives.

• Experience with Angular 4, which focused on making the framework faster and smaller.

• Familiar with Angular 6, which introduced Angular Elements and Angular CLI v6.

• Proficient in Angular 8, which brought improvements in Ivy rendering engine and differential loading.

• Hands-on experience with Angular 10, which introduced stricter types and imp...read more

Ngrx is a state management library for Angular, while RxJS is a reactive programming library for handling asynchronous data streams.

• Ngrx is built on top of RxJS and uses its observables for state management.

• RxJS provides operators for handling asynchronous events, while Ngrx provides a structured way to manage application state.

• Example: In Ngrx, actions are dispatched to modify the state, whereas in RxJS, you can use operators like map, filter, and merge to transform data str...read more

Custom pipes in Angular are used to transform data in templates.

• Custom pipes are created using the @Pipe decorator in Angular.

• To use a custom pipe in HTML, you need to include it in the declarations array of the NgModule.

• You can pass parameters to custom pipes in HTML using the pipe symbol (|).

• Example: {{ value | customPipe:param1:param2 }}

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 duplicates all levels of nested objects, while shallow copy only duplicates the top level object.

• Deep copy creates a completely new object with its own memory space, while shallow copy creates a new object that references the same memory locations as the original object.

• Deep copy is more memory intensiv...read more

Handle errors in fetching API calls by implementing error handling mechanisms.

• Use try-catch blocks to catch errors during API calls

• Implement error handling logic in the catch block to handle different types of errors

• Display user-friendly error messages to inform users about the issue

• Use HTTP status codes to identify the type of error (e.g. 404 for not found)

• Implement retry mechanisms for temporary network issues

Denouncing and throttling are techniques used to control the rate at which a function is called.

• Denouncing is the practice of ignoring repeated calls to a function until a certain amount of time has passed.

• Throttling limits the rate at which a function can be called, ensuring it is not called more than once within a specified time interval.

• These techniques are commonly used in front-end development to optimize performance and prevent excessive function calls.

• Example: Denounci...read more

Arrow functions are concise and do not bind their own 'this' value, while regular functions have their own 'this' value and can be used as constructors.

• Arrow functions have a more concise syntax compared to regular functions.

• Arrow functions do not have their own 'this' value, they inherit it from the parent scope.

• Regular functions have their own 'this' value, which can be useful for object-oriented programming and constructor functions.

ForkJoin is an operator in Angular that allows for parallel execution of multiple observables.

• ForkJoin combines the values from multiple observables and emits them as an array when all observables complete.

• It waits for all observables to complete and then emits the combined result.

• Example: forkJoin([observable1, observable2]).subscribe(result => console.log(result));

Wildcard routes in Angular allow for handling unknown routes and redirecting to a default route.

• Wildcard route is denoted by '**' in the route configuration.

• It is typically used at the end of the route configuration to handle unknown routes.

• Example: { path: '**', redirectTo: '/404' }

Session Storage is a web storage API that allows data to be stored and accessed during a single session.

• Session Storage is a type of web storage that stores data for a single session only.

• Data stored in Session Storage is accessible only within the same tab or window.

• Session Storage data is cleared when the tab or window is closed.

• Session Storage is useful for storing temporary data that needs to be available during a user's visit to a website.

Compilation process is the process of converting source code into machine code by a compiler.

• Source code is written in a high-level language like TypeScript or JavaScript.

• Compiler translates the source code into intermediate code.

• Intermediate code is then converted into machine code by the compiler.

• Compilation process checks for syntax errors and generates executable code.

• Examples of compilers include Angular CLI for Angular applications and TypeScript compiler for TypeScript...read more

Angular Architecture is a structural design of Angular applications that includes components, modules, services, and routing.

• Angular applications are built using components, which are reusable building blocks with their own logic and templates.

• Modules help organize the application into cohesive blocks of functionality.

• Services are used for sharing data and functionality across components.

• Routing allows navigation between different components based on the URL.

• Angular follows a...read more

There are two types of compilations in Angular: Just-in-Time (JIT) compilation and Ahead-of-Time (AOT) compilation.

• Just-in-Time (JIT) compilation: Compiles the Angular application in the browser at runtime. Slower startup time but easier development process.

• Ahead-of-Time (AOT) compilation: Compiles the Angular application during the build process before the browser downloads and runs the code. Faster startup time but requires more setup and configuration.

ES6 features are modern JavaScript enhancements that improve code readability and efficiency.

• 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 = 'John'; console.log(`Hello, ${name}!`);

• Destructuring assignment for easily extracting values from arrays or objects: const { firstName, lastName } = person;

• Spread syntax for merging arrays or objects:...read more

Subject vs BehaviourSubject in Angular

• Subject is a basic observable that emits values to subscribers

• BehaviourSubject is a type of Subject that stores the latest value and emits it to new subscribers

• BehaviourSubject requires an initial value when created

Shallow copy only copies the references of nested objects, while deep copy creates new copies of nested objects.

• Shallow copy creates a new object but does not create copies of nested objects.

• Deep copy creates a new object and also creates copies of nested objects.

• Shallow copy is faster and more memory efficient, but changes to nested objects affect both original and copied objects.

• Deep copy is slower and consumes more memory, but changes to nested objects do not affect the or...read more

Angular is a popular open-source web application framework developed by Google for building dynamic single-page applications.

• Angular is based on TypeScript, a superset of JavaScript.

• It uses components to build the user interface.

• Angular provides features like data binding, dependency injection, and routing.

• It has a powerful CLI for scaffolding and managing projects.

• Angular is commonly used for building interactive web applications.

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

• Routing allows users to navigate between different parts of an Angular application without reloading the entire page.

• Routes are defined in the app-routing.module.ts file using the RouterModule and Routes classes.

• Each route maps a URL path to a component, which is then displayed when the corresponding URL is accessed.

• Angular Router provides features like route guards, lazy lo...read more

Building blocks of Angular include components, modules, services, directives, templates, and dependency injection.

• Components are the basic building blocks of Angular applications

• Modules help organize the application into cohesive blocks of functionality

• Services are reusable code that can be injected into components

• Directives add behavior to elements in the DOM

• Templates define the UI of the application

• Dependency injection is a design pattern used to increase efficiency and mod...read more

Angular life cycle includes initialization, change detection, content projection, and destruction.

• Initialization: ngOnInit is called after the component is initialized.

• Change Detection: Detects changes in component properties and updates the view.

• Content Projection: Projects external content into the component.

• Destruction: ngOnDestroy is called before the component is destroyed.