Codes For Tomorrow Front end Developer Interview Questions and Answers

Q1. Hoisting concept with examples and guess the output
Ans. 
Hoisting is a JavaScript mechanism where variable and function declarations are moved to the top of their containing scope.
• Variable declarations are hoisted but not their initializations.

• Function declarations are fully hoisted.

• Example: console.log(myVar); var myVar = 10; // Output: undefined

• Example: console.log(myFunc()); function myFunc() { return 'Hello!'; } // Output: Hello!
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Q2. Map functionality with a call back function
Ans. 
Using map function to apply a callback function to each element in an array
• Map function is used to iterate over an array and apply a callback function to each element

• The callback function can perform operations on each element and return a new value

• Example: arr.map(item => item * 2) will double each element in the array
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Q3. Copy object, spread operator usage . Deep copy, sallow copy
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Q4. Flexbox vs grid, dom, box model,
Ans. 
Flexbox is best for one-dimensional layouts, Grid is best for two-dimensional layouts, DOM is the structure of a webpage, Box model is the layout of elements.
• Flexbox is best for creating one-dimensional layouts like navigation bars or sidebars.

• Grid is best for creating two-dimensional layouts like grids of images or cards.

• DOM (Document Object Model) is the structure of a webpage, representing the elements as objects.

• Bo...read more
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Q5. React optimization, why React,
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Q1. Mostly js questions, not so many of angular or react.
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Q2. Like fizbuzz or things like that.
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Coding a frontend UI from provided image. And creating a fucntional star rating system

Q1. Designing a Component API in React using Typescript.
Ans. 
Designing a Component API in React using Typescript involves defining props, state, and methods for the component.
• Define the props interface to specify the expected input data for the component

• Use typescript types to ensure type safety and prevent runtime errors

• Define the state interface to manage the internal state of the component

• Implement methods to handle user interactions and component logic

• Document the component
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Q2. Create a function that can clear all the timer ids at once.
Ans. 
Function to clear all timer ids at once
• Create an array to store all timer ids

• Iterate through the array and clear each timer id using clearTimeout() function
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Q1. Introduction life cycle looks pipe @input @output
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Q1. What is event bubbling
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Q2. What is TDD and why TDD
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Reactive form and crud operations pipes crud operations

Q1. Basic understanding of js and angular is must expeciallly how js works questions on arrays objects shallow deep copy
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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. It was a array question. I was told to return a object from a function which would contain getting all the array elements, adding a element, deleting a element. The test was on hacker rank.
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Q1. This was basically a one on one round. I was asked basics of HTML, CSS and React. Questions like Hoisting, Prop Drilling, Context API. Not only do you need to know what the topics are. But I was asked to i...read more
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Q1. Basic Company Details and Salary Negotiations
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