Citicon Engineers Interview Questions and Answers

Unable to login with correct credentials

• Entered correct username and password

• Clicked on login button

• Error message displayed: 'Invalid username or password'

Test case for apple

• Verify the apple is not rotten or spoiled

• Check the weight and size of the apple

• Ensure the apple is not bruised or damaged

• Test the sweetness and texture of the apple

• Confirm the apple is free from pesticides and chemicals

No, it is not advisable to use indexes as keys in React components.

• Using indexes as keys can lead to performance issues and incorrect behavior when reordering or deleting items in a list.

• It is recommended to use unique IDs as keys to ensure proper component rendering and reconciliation.

• Example:

  {items.map((item, index) =>
  • {item}
  )}

Memoisation should be used to optimize performance by caching expensive function calls.

• Use memoisation when a function is computationally expensive and its output depends only on its input parameters.

• Memoisation can be used to cache the results of recursive function calls to avoid redundant calculations.

• In React, useMemo hook can be used to memoize the result of a function component to prevent unnecessary re-renders.

• Memoisation is particularly useful in optimizing performance...read more

Hooks are a new addition in React 16.8 that allow you to use state and other React features without writing a class.

• Hooks are functions that let you use state and other React features in functional components.

• They allow you to reuse stateful logic without changing your component hierarchy.

• Examples of hooks include useState, useEffect, useContext, etc.

Hoisting is a JavaScript mechanism where variable and function declarations are moved to the top of their containing scope.

• Variable and function declarations are hoisted to the top of their scope during the compilation phase.

• Only declarations are hoisted, not initializations.

• Function declarations are hoisted before variable declarations.

Keys are unique identifiers for elements in a list in React, used for efficient rendering and updating.

• Keys help React identify which items have changed, are added, or are removed in a list.

• Keys should be unique among siblings, but don't need to be globally unique.

• Using index as a key is not recommended as it can cause issues with component state.

• Keys are important for performance optimization in React.

• Example:

  {items.map((item) =>
  • {item.name}
  )}

Code splitting is a technique used to split a large bundle of code into smaller chunks that can be loaded on demand.

• Code splitting helps improve performance by reducing initial load times.

• It allows for lazy loading of code, meaning only the necessary code is loaded when needed.

• Commonly used in React applications using dynamic imports or React.lazy().