10+ Qcon Interview Questions and Answers

Delegates are reference types that hold a reference to a method. They are used to achieve loose coupling and extensibility.

• Delegates allow methods to be passed as parameters to other methods.

• They can be used to implement callbacks and event handlers.

• Delegates can be multicast, meaning they can hold references to multiple methods.

• There are two types of delegates: singlecast and multicast.

Base href in index.html is used to specify the base URL for all relative URLs in the document.

• Base href is used to set the base URL for all relative URLs in the document.

• It is helpful when working with multiple directories or when the website is hosted on a subdirectory.

• Example: <base href='https://www.example.com/'>

Multicasting in Angular is a technique to broadcast a single stream of data to multiple subscribers.

• It allows multiple subscribers to receive the same data stream.

• It reduces the number of HTTP requests made by the application.

• It can be achieved using RxJS operators like multicast() and refCount().

Component interaction is the process of communication and data exchange between different software components.

• Components can interact through APIs, events, or shared memory.

• APIs allow components to expose their functionality to other components.

• Events enable components to notify each other of changes or trigger actions.

• Shared memory allows components to access and modify the same data.

• Component interaction is crucial for building complex software systems.

Two way binding is a technique used in software development to keep data synchronized between the model and the view.

• Two way binding allows changes made to the model to be reflected in the view and vice versa.

• It is commonly used in front-end frameworks like Angular and React.

• In Angular, two way binding is achieved using [(ngModel)] directive.

• In React, two way binding can be achieved using state and props.

• Two way binding can improve user experience by reducing the need for man...read more

Polyfills are code that allows modern browsers to support features that are not natively supported.

• Polyfills are used to bridge the gap between modern web development and older browsers.

• They provide a way to use new features without worrying about browser compatibility.

• Polyfills can be used for features like CSS Grid, Fetch API, and ES6 syntax.

• They are often included in JavaScript libraries and frameworks like React and Angular.

Connection pooling is a technique of reusing database connections to improve performance.

• Connection pooling helps to reduce the overhead of creating and closing database connections.

• It maintains a pool of database connections that can be reused by multiple clients.

• It improves the scalability and performance of the application.

• Connection pooling can be configured with parameters like maximum pool size, timeout, etc.

• Examples of connection pooling libraries are HikariCP, Apache ...read more

SOLID principles are a set of five design principles for writing maintainable and scalable code.

• S - Single Responsibility Principle

• O - Open-Closed Principle

• L - Liskov Substitution Principle

• I - Interface Segregation Principle

• D - Dependency Inversion Principle

Generations of Garbage collection are used to manage memory in Java applications.

• Garbage collection is the process of automatically freeing up memory that is no longer in use by the application.

• Generational garbage collection divides objects into different generations based on their age and usage patterns.

• Young generation is where new objects are created and old objects that survive multiple garbage collections are moved to the old generation.

• Old generation is where long-live...read more

API versioning is the process of managing and updating different versions of an API.

• API versioning allows developers to make changes to an API without breaking existing client applications.

• It involves assigning a version number to each release of the API.

• Versioning can be done through URL paths, headers, or query parameters.

• Examples of API versioning include Twitter API v1.1 and Google Maps API v3.

• API versioning is important for maintaining backwards compatibility and ensurin...read more

Prevent SQL Injection by using parameterized queries and input validation.

• Use parameterized queries instead of concatenating user input with SQL statements.

• Sanitize user input by validating and escaping special characters.

• Limit database user privileges to only necessary actions.

• Implement web application firewalls to detect and block SQL injection attempts.

• Regularly update and patch software to fix known vulnerabilities.

Route guards are used in Angular to prevent unauthorized access to certain routes.

• Route guards can be used to check if a user is authenticated before allowing access to a route.

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

• CanActivate is used to protect individual routes, while CanActivateChild is used to protect child routes.

• CanLoad is used to prevent lazy-loaded modules from being loaded until certain conditions are met.

Life cycle hooks are methods that allow you to tap into the lifecycle of a component in Angular.

• Life cycle hooks are used to perform actions at specific stages of a component's lifecycle.

• There are eight different life cycle hooks in Angular.

• Examples of life cycle hooks include ngOnInit, ngOnChanges, and ngOnDestroy.

AOT stands for Ahead of Time compilation, a technique used to compile code before it is executed.

• AOT is used to improve the performance of applications by compiling code before it is executed.

• It is commonly used in mobile app development to reduce app startup time.

• AOT can also help to reduce the size of the application binary.

• Examples of AOT compilers include Google's Android Runtime (ART) and Apple's LLVM-based compiler.

IEnumerable is in-memory collection while IQueryable is a queryable data source.

• IEnumerable is used for querying data from in-memory collections like List, Array, etc.

• IQueryable is used for querying data from a database or remote data source.

• IQueryable supports deferred execution while IEnumerable does not.

• IQueryable allows for filtering, sorting, and paging to be done on the server side.

• IQueryable is more efficient when dealing with large datasets.

Observables are streams of data while Promises are one-time operations.

• Observables can emit multiple values over time while Promises can only resolve once.

• Observables can be cancelled while Promises cannot.

• Observables are lazy while Promises are eager.

• Observables can handle errors within the stream while Promises require a catch block.

• Observables are used in reactive programming while Promises are used in asynchronous programming.