Belcan Reactjs Developer Interview Questions and Answers

Q1. What is client side and server side rendering
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Q1. Flat the array without using the inbuilt methods
Ans. 
Flatten an array without using inbuilt methods
• Use recursion to iterate through the array and flatten it

• Create a new array to store the flattened elements

• Check if each element is an array, if so, recursively call the function to flatten it
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Q2. Sort the given objects based on the ages
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Q1. What is the difference between states and props ?
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States are mutable data managed within a component, while props are immutable data passed from parent to child components.
• States are managed within a component and can be changed using setState method

• Props are passed from parent to child components and are immutable

• States are used for internal component data management, while props are used for passing data between components

• Example: A counter component may have a stat...read more
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Q2. How are data passed from children to parents in react component?
Ans. 
Data can be passed from children to parents in React components by using callback functions.
• Use callback functions to pass data from child components to parent components

• Parent component passes a function as a prop to child component

• Child component calls the function with the data as an argument to pass data to parent component
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Progress bar in react and remote data fetching

Q1. Ui related questions
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Q1. Asked for preferred location and salary
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Q1. Splice & slice difference
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Splice is used to add/remove elements from an array, while slice is used to extract a portion of an array without modifying the original array.
• Splice modifies the original array, while slice does not.

• Splice can add elements, remove elements, or replace elements in an array.

• Slice returns a new array with the selected elements from the original array.

• Example: const arr = [1, 2, 3, 4, 5]; arr.splice(2, 1); // removes elem...read more
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Q2. Coding question | How to reverse string
Ans. 
To reverse a string, iterate through the characters and swap them from start to end.
• Create an empty string to store the reversed result.

• Iterate through the characters of the input string from end to start.

• Append each character to the empty string to reverse the order.

• Return the reversed string.
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Q1. What is Pure components/memo/useCallback/HoC
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Pure components, memo, useCallback, and HoC are optimization techniques in React for improving performance.
• Pure components are components that only re-render when their props or state change.

• memo is a higher order component that memoizes the result of a component rendering, preventing unnecessary re-renders.

• useCallback is a hook that memoizes functions, preventing unnecessary re-creations on re-renders.

• HoC (Higher Orde...read more
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Q1. Javascript array methods like filter and reduce. Javascript guess the output questions based on variables and functions.
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Q2. React lifecycle methods
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Q3. UseState and useEffect usecase
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Q1. What is closures, Hoisting with example Semantic elements
Ans. 
Closures and hoisting are important concepts in JavaScript.
• Closures refer to the ability of a function to access variables in its outer scope even after the function has returned.

• Hoisting is the behavior of moving variable and function declarations to the top of their respective scopes.

• Example of closures: function outer() { let x = 10; function inner() { console.log(x); } return inner; } const innerFunc = outer(); inn...read more
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Q2. Chaining Methods Currying Call bind and apply Optimization of application Server side rendering
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Q3. Selectors HTML 5 features
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