Junior Web Developer Interview Questions and Answers for Freshers

Real DOM is the actual DOM in the browser, while Virtual DOM is a lightweight copy used for performance optimization.

• Real DOM updates are slow and inefficient due to direct manipulation of the actual DOM elements.

• Virtual DOM is a virtual representation of the actual DOM, allowing for faster updates and improved performance.

• React uses Virtual DOM to update only the necessary parts of the actual DOM, reducing unnecessary re-renders.

Closure is a function that has access to its own scope, even after the function has closed.

• Closure allows a function to access and manipulate variables from its outer scope.

• Use closure when you want to create private variables or functions that are only accessible within a specific scope.

• Example: Creating a counter function using closure to maintain the count state.

Promises in JavaScript are objects representing the eventual completion or failure of an asynchronous operation.

• Promises help to handle asynchronous operations in a more organized and readable way.

• They can be in one of three states: pending, fulfilled, or rejected.

• Promises can be chained together using .then() to handle success and .catch() to handle errors.

• Example: const myPromise = new Promise((resolve, reject) => { ... });

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Props are a way to pass data from a parent component to a child component in React.

• Props are read-only and cannot be modified by the child component.

• Props are passed down from parent to child components through attributes.

• Props can be any type of data, including strings, numbers, arrays, objects, or functions.

• Example: <ChildComponent name='John' age={25} />

HOC (Higher Order Component) in Reactjs is a pattern where a function takes a component and returns a new component.

• HOC allows code reuse, logic abstraction, and props manipulation in React components.

• Example: withAuth HOC can be used to restrict access to certain components based on user authentication.

• HOC can be created using a function that takes a component as an argument and returns a new component with additional props or functionality.

OOPs (Object-Oriented Programming) is a programming paradigm based on the concept of objects, which can contain data and code.

• OOPs focuses on creating reusable code through classes and objects

• Encapsulation: bundling data and methods that operate on the data within a single unit

• Inheritance: allows a class to inherit properties and behavior from another class

• Polymorphism: ability for objects to be treated as instances of their parent class or their own class

• Abstraction: hiding ...read more