Impact Analytics Senior Front end Developer Interview Questions and Answers

Decent questions asked in the online mcq test

Q1. Redux vs context API
Ans. 
Redux is a predictable state container for JavaScript apps, while Context API is a feature in React for passing data through the component tree.
• Redux is more suitable for larger applications with complex state management needs.

• Context API is simpler to use and is built into React, reducing the need for additional libraries.

• Redux provides a single source of truth for the application state, making it easier to debug and ...read more
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Round duration - 60 Minutes
Round difficulty - Medium

Q1. 
Last Stone Weight Problem Explanation
Given a collection of stones, each having a positive integer weight, perform the following operation: On each turn, select the two heaviest stones and smash them toge...read more
Ans. 
This question is about finding the weight of the last stone after repeatedly smashing the two heaviest stones together.
• Sort the array of stone weights in descending order.

• Repeatedly smash the two heaviest stones until there is at most 1 stone left.

• If there is 1 stone left, return its weight. Otherwise, return 0.
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Round duration - 60 minutes
Round difficulty - Medium

Q1. Design a sign-in page using only HTML and CSS.
Ans. 
A signin page designed using HTML and CSS only.
• Create a form element to contain the signin inputs

• Use appropriate input types for email and password fields

• Apply CSS styles to align and format the signin page

• Add a submit button to trigger the signin action
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Round duration - 7 days
Round difficulty - Medium

Q1. How would you design and develop a to-do list application using local storage?
Ans. 
A todo list application using localstorage.
• Use HTML, CSS, and JavaScript to create the user interface.

• Use the localstorage API to store and retrieve todo items.

• Implement features like adding, editing, and deleting todo items.

• Display the list of todo items and their status.

• Allow users to mark todo items as completed or incomplete.
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Round duration - 120 Minutes
Round difficulty - Easy

Round duration - 60 Minutes
Round difficulty - Easy

Questions related to react and high level javascript?

Q1. What is hoisting in JavaScript?
Ans. 
Hoisting is a JavaScript behavior where variable and function declarations are moved to the top of their containing scope.
• Hoisting applies to both variable and function declarations.

• Variable declarations are hoisted but not their initializations.

• Function declarations are fully hoisted, including their definitions.

• Hoisting can lead to unexpected behavior if not understood properly.
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Q2. What is memoization in JavaScript?
Ans. 
Memoization is a technique in JavaScript to cache the results of expensive function calls for future use.
• Memoization improves performance by avoiding redundant calculations

• It is commonly used in recursive functions or functions with expensive computations

• The cached results are stored in a data structure like an object or a map

• Memoization can be implemented manually or using libraries like Lodash or Memoizee
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Q3. What is an IIFE (Immediately Invoked Function Expression) in JavaScript?
Ans. 
IIFE stands for Immediately Invoked Function Expression. It is a JavaScript function that is executed as soon as it is defined.
• IIFE is a way to create a function expression and immediately invoke it.

• It helps in creating a private scope for variables and functions.

• It is commonly used to avoid polluting the global namespace.

• IIFE can be written using different syntaxes like using parentheses, function declaration, or arro
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Q4. What are promises in JavaScript?
Ans. 
Promises in JavaScript are objects that represent the eventual completion or failure of an asynchronous operation.
• Promises are used to handle asynchronous operations such as fetching data from a server or reading a file.

• They simplify the process of writing asynchronous code by providing a more structured approach.

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

• They can be chained together using methods like...read more
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Q5. What is the Temporal Dead Zone in JavaScript?
Ans. 
Temporal Dead Zone is a behavior in JavaScript where variables are not accessible before they are declared.
• Temporal Dead Zone occurs when accessing variables before they are declared

• Variables in the Temporal Dead Zone cannot be accessed or assigned

• The Temporal Dead Zone is a result of JavaScript's hoisting behavior

• Example: accessing a variable before it is declared will throw a ReferenceError
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Q6. What are arrow functions in JavaScript?
Ans. 
Arrow functions are a concise way to write functions in JavaScript.
• Arrow functions have a shorter syntax compared to regular functions.

• They do not have their own 'this' value.

• They do not have the 'arguments' object.

• They cannot be used as constructors with the 'new' keyword.

• They are commonly used in functional programming and with array methods like 'map' and 'filter'.
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Q7. What is JSX?
Ans. 
JSX is a syntax extension for JavaScript that allows you to write HTML-like code in your JavaScript files.
• JSX stands for JavaScript XML

• It is commonly used with React to define the structure and appearance of components

• JSX elements are transpiled into regular JavaScript function calls

• It allows you to write HTML-like code with JavaScript expressions embedded within curly braces

• Example:

  Hello, {name}!
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Q8. What are higher-order functions in JavaScript?
Ans. 
Higher order functions are functions that can take other functions as arguments or return functions as their results.
• Higher order functions can be used to create more flexible and reusable code.

• They enable functional programming paradigms.

• Examples of higher order functions include map, filter, and reduce in JavaScript.
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Q9. What is the virtual DOM in JavaScript?
Ans. 
Virtual DOM is a lightweight copy of the actual DOM that allows efficient updates and rendering in JavaScript frameworks.
• Virtual DOM is a concept used in JavaScript frameworks like React.

• It is a lightweight copy of the actual DOM tree.

• Changes made to the virtual DOM are compared with the actual DOM to determine the minimal updates needed.

• This helps in efficient rendering and improves performance.

• Virtual DOM allows deve...read more
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Round duration - 35 Minutes
Round difficulty - Easy

Happend around 08:30 pm

Given the task to complete page design.

Q1. Create a Todo app
Ans. 
A simple Todo app to manage tasks and deadlines
• Create a form to add new tasks

• Display a list of tasks with checkboxes to mark as complete

• Include options to edit or delete tasks

• Implement functionality to mark tasks as complete or incomplete

• Add a feature to filter tasks by status (completed/incomplete)
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Q2. Lifecycle methods
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Round duration - 90 Minutes
Round difficulty - Easy

You are given three ds coding questions which you have to solve within 90 mins.
The questions are easy to medium level for this round

Q1. 
Non-Decreasing Array Problem Statement
Given an integer array ARR of size N, determine if it can be transformed into a non-decreasing array by modifying at most one element.
An array is defined as non-de...read more
Ans. 
The solution checks if an integer array can become non-decreasing by modifying at most one element.
• Iterate through the array and check if there are more than one decreasing pairs of elements.

• If there are more than one decreasing pairs, return false.

• If there is only one decreasing pair, check if modifying one of the elements can make the array non-decreasing.

• If modifying the element at index i-1 or i can make the array ...read more
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Q2. 
Sort Linked List Based on Actual Values
You are given a Singly Linked List of integers that is initially sorted according to the absolute values of its elements. Your task is to sort this Linked List base...read more
Ans. 
The task is to sort a singly linked list based on actual values instead of absolute values.
• Traverse the linked list and store the values in an array

• Sort the array using any sorting algorithm

• Create a new linked list using the sorted array

• Return the new linked list
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Q3. 
Diameter of a Binary Tree Problem Statement
Given a binary tree, return the length of its diameter. The diameter of a binary tree is defined as the length of the longest path between any two nodes in the ...read more
Ans. 
The diameter of a binary tree is the length of the longest path between any two end nodes in the tree.
• The diameter of a binary tree can be calculated by finding the maximum of the following three values: 1) the diameter of the left subtree, 2) the diameter of the right subtree, and 3) the longest path that passes through the root node.

• To find the diameter of a binary tree, we can use a recursive approach. We calculate ...read more
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Round duration - N/A
Round difficulty - Medium

Round duration - 120 Minutes
Round difficulty - Hard

This round focus on advanced Js concepts and the tech stack I used in my projects.

Q1. 
Find Unique Element in Array
You have been provided an integer array/list ARR of size N. Here, N is equivalent to 2M + 1 where each test case has M numbers appearing twice and one number appearing exactly...read more
Ans. 
The task is to find the unique number in an array where all other numbers occur twice.
• The array size is given by N = 2M + 1, where M is the number of elements occurring twice.

• Loop through the array and use a hashmap to count the occurrences of each number.

• Return the number with a count of 1, as it is the unique number.
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Round duration - 60 Minutes
Round difficulty - Easy

It was a late night round as i have already had the previous 3 rounds at the same day. The HR asked about my experience regarding the previous rounds and also some situation based questions.

Focused on JS questions

Q1. React concept explain
Ans. 
React is a JavaScript library for building user interfaces.
• React is a declarative, efficient, and flexible JavaScript library for building user interfaces.

• It allows developers to create reusable UI components.

• React uses a virtual DOM to improve performance by only updating the necessary parts of the actual DOM.

• React follows a unidirectional data flow, making it easier to understand how data changes over time.

• React can ...read more
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- They use their own platform for interviews, and assessments.
- There were html, css, js based questions in the coding round.
- Some questions were theoretical too.
- They tested nearly all major parts of js including let, const, arrays, promise, async, await, events, lexical scope, etc.

Q1. It was an online machine coding round, where you have to build something they ask in 1hr using html, css, js (vanilla).
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Q1. Focused on html, css, and js (basic)
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Q1. Focus majorly on JS some quick demonstration, advanced concepts like closures, async nature of js, etc
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Q1. Behavioral round
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