Successive Technologies Interview Questions and Answers

The Event Loop is a core concept in JavaScript that enables non-blocking I/O operations, allowing asynchronous programming.

• JavaScript is single-threaded, meaning it can execute one command at a time.

• The Event Loop manages the execution of code, collecting and processing events, and executing queued sub-tasks.

• When an asynchronous operation (like a network request) is initiated, it runs in the background, freeing the mai...read more

forEach and map are both array methods in JavaScript, but they differ in their return values and usage.

• forEach executes a provided function once for each array element and does not return anything.

• map creates a new array with the results of calling a provided function on every element in the array.

• forEach is used when we want to perform an action on each element of the array, while map is used when we want to transform...read more

Rest and spread operators are used in JavaScript to manipulate arrays and objects.

• Rest operator allows us to represent an indefinite number of arguments as an array.

• Spread operator allows us to spread an array or object into individual elements.

• Rest operator is denoted by three dots (...)

• Spread operator is also denoted by three dots (...) but is used in a different context.

• Rest operator can be used in function paramete...read more

Closures are functions that have access to variables in their outer scope, even after the outer function has returned.

• Closures are created when a function is defined inside another function.

• The inner function has access to the outer function's variables and parameters.

• Closures can be used to create private variables and methods in JavaScript.

• Closures can also be used to create functions with pre-set arguments.

Call, apply, and bind are methods used to manipulate the 'this' keyword in JavaScript functions.

• Call invokes a function with a specified 'this' value and arguments provided individually.

• Apply invokes a function with a specified 'this' value and arguments provided as an array.

• Bind returns a new function with a specified 'this' value and initial arguments.

• All three methods are used to control the value of 'this' in a fun...read more

Hoisting is a JavaScript mechanism where variables and function declarations are moved to the top of their scope.

• Variables declared with var are hoisted to the top of their scope

• Function declarations are also hoisted to the top of their scope

• Function expressions are not hoisted

• Hoisting can lead to unexpected behavior and bugs

for of loop is used to iterate over iterable objects while for in loop is used to iterate over object properties.

• for of loop is used with arrays, strings, maps, sets, etc.

• for in loop is used with objects to iterate over its properties.

• for of loop returns the values of the iterable object while for in loop returns the keys of the object properties.

• for of loop cannot be used with plain objects while for in loop can be us...read more

Dependency injection is a design pattern that allows objects to receive dependencies rather than creating them internally.

• Dependency injection is a way to achieve loose coupling between objects.

• It allows for easier testing and maintenance of code.

• There are three types of dependency injection: constructor injection, setter injection, and interface injection.

• Example: Instead of creating a database connection object insid...read more

Angular project starts with creating a new project using Angular CLI.

• Install Angular CLI globally using npm

• Create a new project using ng new command

• Serve the project using ng serve command

• Open the project in a browser at http://localhost:4200/

package.json is a file used in Node.js projects to manage dependencies and scripts.

• Contains metadata about the project

• Lists dependencies and devDependencies

• Scripts for running tasks

• Version of Node.js required

• Author and license information

Services in Angular are singleton objects that provide functionality to components. Observables are used for asynchronous data streams.

• Services are used to share data and functionality across components

• Services are singleton objects that can be injected into components

• Observables are used for asynchronous data streams

• Observables can be subscribed to in order to receive data

• Observables can emit multiple values over time

A component is a building block of an Angular application that represents a part of the UI.

• Components are reusable and can be nested within other components.

• Each component has its own template, styles, and logic.

• Components communicate with each other using inputs and outputs.

• Angular CLI generates components using the command 'ng generate component'.

Observables are streams of data that can be subscribed to, while Promises are one-time operations that return a single value.

• Observables can emit multiple values over time, while Promises can only return a single value.

• Observables can be cancelled, while Promises cannot.

• Observables are lazy, meaning they only emit values when subscribed to, while Promises are eager and immediately execute when created.

• Observables have ...read more

Promises are a way to handle asynchronous operations in JavaScript.

• Promises represent a value that may not be available yet, but will be resolved at some point in the future.

• They have three states: pending, fulfilled, or rejected.

• Promises can be chained together using .then() and .catch() methods.

• They help avoid callback hell and make code more readable and maintainable.

• Example: fetch() API returns a Promise that resol...read more

Callbacks are functions passed as arguments to another function to be executed later.

• Callbacks are commonly used in asynchronous programming.

• They allow for non-blocking execution of code.

• Callbacks can be anonymous or named functions.

• Example: setTimeout(function() { console.log('Hello, world!'); }, 1000);

Callback hell is a situation where nested callbacks make code difficult to read and maintain.

• Use named functions instead of anonymous functions

• Use Promises or async/await to handle asynchronous operations

• Use modularization and separation of concerns to break down complex code

• Use error handling to prevent code from breaking

Async/await is a way to write asynchronous code in a synchronous style.

• Async/await is a syntax for writing asynchronous code in JavaScript.

• It allows you to write asynchronous code that looks like synchronous code.

• It uses the 'async' keyword to define an asynchronous function and the 'await' keyword to wait for a promise to resolve.

• It helps to avoid callback hell and makes code more readable and maintainable.

CSS Box model is a design concept that describes how elements are displayed on a webpage.

• It consists of content, padding, border, and margin.

• Content is the actual element content, padding is the space between content and border, border is the element's border, and margin is the space between border and other elements.

• The box model can be adjusted using CSS properties such as padding, border, and margin.

• Understanding th...read more

Flexbox is a CSS layout module that allows you to easily align and distribute space among items in a container.

• Flexbox is used for creating responsive and flexible layouts.

• It allows you to specify how much space each item should take up in a container.

• You can align items vertically and horizontally using flexbox properties.

• Flexbox is supported by all modern browsers.

• Example: display: flex; justify-content: center; alig...read more

Keyframes are markers in time used for animation.

• Keyframes define the starting and ending points of an animation.

• They can also define intermediate points for more complex animations.

• CSS and JavaScript both use keyframes for animation.

• Example: @keyframes in CSS or the Keyframe API in JavaScript.

Media queries are CSS rules that apply different styles based on the device's screen size, orientation, and resolution.

• Media queries are used to create responsive web designs.

• They allow developers to target specific devices and adjust the layout accordingly.

• Media queries use the @media rule in CSS.

• Examples of media queries include adjusting font sizes, hiding or showing elements, and changing the layout.

• Media queries c...read more