ONE BCG Front end Developer Interview Questions and Answers

Q1. Merge sort time complexity less
Ans. 
Merge sort has a time complexity of O(n log n) in the worst case scenario.
• Merge sort divides the array into two halves, sorts them recursively, and then merges them back together.

• The time complexity of merge sort is O(n log n) in the worst case scenario.

• For example, sorting an array of 8 elements would take 3 recursive calls to merge sort.
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Q2. Palindrome with react js to show on UI
Ans. 
Create a palindrome checker using React JS to display on the UI
• Create a input field for user to enter a string

• Use state to store the input string

• Create a function to check if the input string is a palindrome

• Display the result on the UI
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Javascript question on promise, callbacks, hosting

Q1. Array linked list queue
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Q1. Fir arrow function This keyword Promises Promise chain Generator function Rest operator Spread operator React hooks Higher order component Redux life cycle Palindrome string code Fibonacci code
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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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90 minutes 3 coding questions

Q1. Wall the topics rite a code using of OOPS
Ans. 
Object-oriented programming (OOP) is a programming paradigm based on the concept of objects, which can contain data and code.
• Create classes to represent real-world entities

• Encapsulate data and behavior within classes

• Use inheritance to create relationships between classes

• Implement polymorphism to allow objects to be treated as instances of their parent class
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Q2. Polymorphism code using all the properties
Ans. 
Polymorphism allows objects of different classes to be treated as objects of a common superclass.
• Polymorphism is achieved through method overriding in subclasses.

• It allows for more flexibility and reusability in code.

• Example: Animal superclass with subclasses Dog and Cat, both overriding the makeSound() method.
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Q3. Inheritance and its types
Ans. 
Inheritance is a mechanism in object-oriented programming where a class inherits properties and behaviors from another class.
• Types of inheritance include single inheritance, where a class inherits from only one parent class

• Multiple inheritance, where a class inherits from multiple parent classes (not supported in some languages)

• Multilevel inheritance, where a class inherits from a class that itself inherits from anothe...read more
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Q1. Tell me about yourself
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Q2. Basic hr questions only
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2 moderate DSA questions and a Question on React on Api's to fetch data

Q1. Reverse given array
Ans. 
Reverse the given array of strings
• Use the reverse() method to reverse the array in place

• Alternatively, you can use a for loop to iterate through the array and build a new reversed array
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Q1. Call api and print data in using react
Ans. 
To call an API and print data in React, use fetch or axios to make the API call and then render the data in the component.
• Use fetch or axios to make the API call in React component

• Store the API response data in state using useState hook

• Render the data in the component using JSX
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Q1. Explain promise in javascript
Ans. 
Promises in JavaScript are objects representing the eventual completion or failure of an asynchronous operation.
• Promises are used to handle asynchronous operations in JavaScript.

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

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

• Example: new Promise((resolve, reject) => { ... }).then(result => { ... }).catch(error =>
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Q2. HTML and CSS basic question
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Q3. Let and var difference
Ans. 
let is block scoped, var is function scoped
• let is block scoped, var is function scoped

• let can't be re-declared in the same scope, var can be

• let variables are not hoisted, var variables are hoisted
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Q4. Spread and rest operator
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Q5. Jwt and interceptor concepts
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