Blackrock 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. 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. Array linked list queue
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Q1. What are closures with examples ?
Ans. 
Closures are functions that have access to their own scope, as well as the scope in which they were defined.
• Closures allow functions to access variables from their outer function even after the outer function has finished executing.

• Closures are commonly used in event handlers and callbacks.

• Example: function outerFunction() { let outerVar = 'I am outer'; return function innerFunction() { console.log(outerVar); }; }
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Q2. How to get updated content on scroll on e-commerce app?
Ans. 
Use infinite scrolling to fetch new content as user scrolls down the page.
• Implement infinite scrolling to load more products as user scrolls down

• Make AJAX calls to fetch new content from the server

• Update the DOM with the new content dynamically
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Javascript array questions like palindrom and others with aptitude

Q1. Skill related technical questions
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Q2. How to share data in components react
Ans. 
Data can be shared between components in React using props, context, or state management libraries like Redux.
• Use props to pass data from parent to child components

• Use context to share data across multiple components without passing props manually

• Use state management libraries like Redux to manage global state and share data between components
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Q3. Prop drilling explain in react
Ans. 
Prop drilling is the process of passing data through multiple levels of components in React.
• Prop drilling occurs when a component needs to pass data to a deeply nested child component.

• It can lead to code that is hard to maintain and understand.

• One way to avoid prop drilling is by using Context API or Redux for state management.
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Q4. Redux flow explain
Ans. 
Redux is a predictable state container for JavaScript apps.
• Redux stores the entire state of an application in a single immutable object.

• State changes are made by dispatching actions, which are plain JavaScript objects.

• Reducers specify how the application's state changes in response to actions.

• Redux flow: Action -> Reducer -> Store -> View
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Q1. Previous project discussion
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Q1. HTML CSS JS Angular React Questions
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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. Tell me about yourself
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