10+ Interview Questions and Answers

Event propagation consists of three stages: capturing, target, and bubbling.

• Capturing phase: Events are captured from the outermost element to the target element.

• Target phase: Event reaches the target element where the event originated.

• Bubbling phase: Events bubble up from the target element to the outermost element.

useReducer is preferred for managing complex state logic, while useState is simpler for basic state management.

• useReducer is more suitable for managing complex state logic and multiple state values

• useState is simpler and more straightforward for basic state management with a single value

• useReducer allows for more organized and centralized state updates through actions and reducers

• useState is commonly used for simple component-level state management

Data can be passed from parent to child components in React using props.

• Pass data as props from parent component to child component

• Use state management libraries like Redux or Context API for complex data sharing

• Use callback functions to pass data from child to parent components

Errors in a React application can be handled by using error boundaries, try-catch blocks, and displaying error messages to users.

• Use error boundaries to catch errors in components and display a fallback UI

• Wrap code that may throw errors in try-catch blocks to handle exceptions

• Use libraries like React Error Boundary to easily implement error handling

• Display error messages to users to inform them about the issue and possible solutions

Error boundary is a React component that catches JavaScript errors anywhere in a component tree and logs those errors.

• Error boundaries are React components that catch JavaScript errors in their child component tree.

• They are used to prevent the entire UI from crashing due to a single error.

• Error boundaries work like a JavaScript catch {} block, but for components.

• They are defined using componentDidCatch lifecycle method.

• Example:

To clone an object in JavaScript, you can use the spread operator or Object.assign() method.

• Use the spread operator to create a shallow copy of an object: const clonedObj = { ...originalObj };

• Use Object.assign() method to create a shallow copy of an object: const clonedObj = Object.assign({}, originalObj);

• For deep cloning, you can use libraries like Lodash or write a custom function to recursively clone nested objects.

Map, filter, and reduce are higher-order functions in JavaScript used to manipulate arrays.

• Map: Transforms each element in an array and returns a new array with the transformed elements.

• Example: [1, 2, 3].map(num => num * 2) returns [2, 4, 6].

• Filter: Returns a new array with elements that pass a certain condition.

• Example: [1, 2, 3].filter(num => num > 1) returns [2, 3].

• Reduce: Applies a function against an accumulator and each element in the array to reduce it to a single val...read more

I have used React hooks such as useState, useEffect, useContext, and useRef in my projects.

• useState

• useEffect

• useContext

• useRef

var and const are used to declare variables in JavaScript, with var being mutable and const being immutable.

• var is used to declare variables that can be reassigned and updated

• const is used to declare variables that cannot be reassigned or updated

• let is another keyword used for declaring variables, similar to var but with block scope

Custom hook to fetch data from an API

• Create a function that uses the useState and useEffect hooks

• Use the fetch API to make a request to the desired endpoint

• Return the fetched data and loading state in an array