EPay Front end Web Developer Interview Questions and Answers for Experienced

Html,css,javascript,reactjs,php,laravel.bootstrap

Q1. Why we use reactjs? and javascript
Ans. 
ReactJS is used for building interactive user interfaces, while JavaScript is the programming language that powers web development.
• ReactJS allows for component-based architecture, making it easier to manage and update UI elements.

• ReactJS uses a virtual DOM for efficient rendering, improving performance.

• JavaScript is the language used to add interactivity and dynamic behavior to web pages.

• JavaScript is essential for cli...read more
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Q2. This is use fro single page web aplication or real time.
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Q1. 1. What is redux? 2. What are useRefs
Ans. 
Redux is a predictable state container for JavaScript apps. useRef is a hook in React for accessing DOM nodes.
• Redux is a state management library for JavaScript applications

• It helps in managing the state of an application in a predictable way

• Redux follows a unidirectional data flow pattern

• useRef is a hook in React that allows accessing DOM nodes or any other mutable value

• It returns a mutable ref object that persists ac
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Q2. What is destructuring
Ans. 
Destructuring is a way to extract values from arrays or objects and assign them to variables.
• Destructuring can be used with arrays and objects

• It allows you to extract values and assign them to variables in a single line of code

• You can also use default values and rename variables during destructuring

• Example: const [a, b] = [1, 2]; // a = 1, b = 2

• Example: const {name, age: years} = {name: 'John', age: 30}; // name = 'Joh
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Q1. What is store in react
Ans. 
Store in React is a centralized state management system.
• Store holds the state of the application.

• It allows components to access and update the state.

• Redux is a popular store implementation for React.

• Context API is another built-in store in React.

• Store helps in managing complex state and makes debugging easier.
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Q1. Interviewer asked about depth in React Js and JavaScript. JavaScript questions - Hoisting, implementation of closure, difference between call, bind & apply. Logic implementation of suggestions list in sea...read more
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Q1. He asked about both technical and non technical related questions. Previous organisation works. What i have faced difficult y in previous organisation. And some scenario based questions.
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Q1. Let var const in JavaScript
Ans. 
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
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Q2. Error boundary and how to handle
Ans. 
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
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Q3. Event.bind and event.property
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Q4. Use of never in typescript
Ans. 
The 'never' type in TypeScript represents a value that will never occur.
• Used to indicate that a function will not return a value

• Commonly used in union types to exclude certain values

• Helps catch potential errors at compile time
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Q5. What hooks you have used
Ans. 
I have used React hooks such as useState, useEffect, useContext, and useRef in my projects.
• useState

• useEffect

• useContext

• useRef
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Q6. What is difference between use reducer and use state
Ans. 
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 co
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Q7. Why we use state and props
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Q8. How you will pass data from parent to child
Ans. 
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
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Q9. Write your own custom hook
Ans. 
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
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Q10. Explain map filter and reduce functions
Ans. 
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 ...read more
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Q11. How you can clone an object
Ans. 
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.
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Q12. What are the three stages of event propagation and how to handle it
Ans. 
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.
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Q13. How to handle errors in your react application
Ans. 
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 poss
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Q14. Write code to call fake api and display the title where category is “some category “
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Q1. What are states and props in React?
Ans. 
States and props are important concepts in React for managing and passing data between components.
• States are mutable data that can be changed within a component

• Props are read-only data passed from parent to child components

• States are managed within a component using setState() method

• Props are accessed using this.props in a component
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Q2. What is Virtual DOM
Ans. 
Virtual DOM is a lightweight copy of the actual DOM that allows for efficient updates and rendering in web applications.
• Virtual DOM is a concept used in frameworks like React to improve performance by minimizing direct manipulation of the actual DOM.

• When changes are made to the virtual DOM, a comparison is done with the actual DOM to determine the minimal updates needed for rendering.

• This process helps reduce the numbe...read more
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Q3. Build a fetch and filter component
Ans. 
A fetch and filter component for data retrieval and manipulation
• Use fetch API to retrieve data from an API endpoint

• Implement a filter function to manipulate the retrieved data based on user input

• Display the filtered data in the UI
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Javascript and React snippets

Q1. Javascipt question
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Q2. Promises, filter, map, What is single page , mulitple page application, opened google page by search for one product in that using console filter it only for sony products only
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Q3. What is DOM, what is the use of that
Ans. 
DOM stands for Document Object Model, it is a programming interface for web documents. It represents the structure of a document as a tree of objects.
• DOM is used to interact with HTML and XML documents in a structured way

• It allows developers to manipulate the content, structure, and style of a website dynamically

• DOM provides methods and properties to access and modify elements on a web page

• Example: document.getElementB...read more
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Q4. What is the output if u type document in console
Ans. 
The output will display the document object in the console.
• Typing 'document' in the console will return the document object, which represents the current HTML document.

• The document object provides access to the content and structure of the webpage, allowing manipulation of elements and properties.
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Q1. Angular lifecycle hooks
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Q2. JS interview questions
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Recurrsion tree implementation with angular

Q1. All about technical questions for SAP Spartacus
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Q1. Salary discussion
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