JPMorgan Chase & Co. React Js Frontend Developer Interview Questions and Answers

Hacker rank test was sent which consisted of react, js, HTML, css, j query and Java questions. You’ve to complete the test in 60 mins

Q1. Promise, closure, diff btw let and const
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Q2. Define virtual dom, viewport, redux, use effect hook
Ans. 
Virtual DOM is a lightweight copy of the actual DOM, viewport is the visible area of a web page, Redux is a state management tool, useEffect hook is used for side effects in React components.
• Virtual DOM is a lightweight copy of the actual DOM, used for efficient updates.

• Viewport is the visible area of a web page on a device's screen.

• Redux is a state management tool for managing application state in a predictable way.

• us...read more
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Q1. React hooks - custom hooks, hooks rules, useEffect vs useLayoutEffect, useReducer Lifecycle with useEffect Context - When, how and why to use it? React 18 new features
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Q2. What does strict mode do? Accessibility in react How forwardRef works? Keys in react controlled components, uncontrolled components, how to use those?
Ans. 
Explaining the features and usage of ReactJS
• Strict mode catches common mistakes and enforces best practices

• ForwardRef allows passing refs to child components

• Keys help React identify which items have changed, added, or removed

• Controlled components are stateful and rely on props to update, while uncontrolled components manage their own state

• Accessibility in React involves using ARIA attributes and semantic HTML
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Q3. ES6 features Shallow cloning and deep cloning How to deep clone nested objects? Hoisting JS execution cycle - call stack, event loop and callbacks
Ans. 
ES6 features, shallow and deep cloning, hoisting, JS execution cycle.
• ES6 features include arrow functions, template literals, let and const, destructuring, spread and rest operators, etc.

• Shallow cloning creates a new object with the same properties as the original object. Deep cloning creates a new object with all nested objects also cloned.

• To deep clone nested objects, use a recursive function or a library like lodash...read more
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Q4. Tell us about a challenging recently faced by you
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Q5. React testing How to test hooks?
Ans. 
Hooks can be tested using React Testing Library or Enzyme.
• Use React Testing Library's renderHook() method to test hooks

• Test the hook's return value and its behavior on re-renders

• Use Enzyme's shallow() or mount() methods to test hooks

• Mock any external dependencies used in the hook

• Test edge cases and error handling
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Round duration - 120 minutes
Round difficulty - Easy

Round duration - 120 minutes
Round difficulty - Easy

Q1. What is the difference between TRUNCATE and DELETE in a database management system?
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Round duration - 30 minutes
Round difficulty - Easy

Q1. 
Triplets with Given Sum Problem
Given an array or list ARR consisting of N integers, your task is to identify all distinct triplets within the array that sum up to a specified number K.
Explanation:
A t...read more
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Round duration - 5 minutes
Round difficulty - Easy