10+ Sintel Systems Interview Questions and Answers

Swap two numbers 'a' and 'b' and output the swapped values.

• Create a temporary variable to store one of the numbers

• Assign the value of 'a' to 'b' and the temporary variable to 'a'

• Output the swapped values as 'b' followed by 'a'

Sort an array of positive integers consisting of 0, 1, and 2 in non-decreasing order.

• Use a counting sort approach to count the occurrences of 0s, 1s, and 2s in the array.

• Update the array with the counts of 0s, 1s, and 2s in order to achieve the sorted array.

• Ensure to handle the constraints of the input array elements being 0, 1, or 2.

• Example: Input: [0, 2, 1, 2, 0], Output: [0, 0, 1, 2, 2]

Promises in JavaScript represent the eventual completion (or failure) of an asynchronous operation.

• Promises are objects that represent the eventual completion (or failure) of an asynchronous operation.

• They have three states: pending, fulfilled, or rejected.

• A pending promise is one that hasn't been fulfilled or rejected yet.

• A fulfilled promise is one that has been successful.

• A rejected promise is one that has encountered an error.

• Promises help in handling asynchronous operatio...read more

Stateless components do not have internal state, while stateful components have internal state that can change.

• Stateless components are functional components that do not have internal state

• Stateful components are class components that have internal state that can change

• Stateless components are simpler and easier to test, while stateful components are more powerful and flexible

• Example: Stateless component - const Button = () => <button>Click me</button>; Stateful component - c...read more

Class components are ES6 classes that extend from React.Component and have state, while functional components are simple functions that take props as arguments.

• Class components are ES6 classes that extend from React.Component

• Functional components are simple functions that take props as arguments

• Class components have state and lifecycle methods, while functional components do not

• Functional components are easier to read, write, and test compared to class components

• With the intr...read more

Top-level directories in Redux should be structured based on functionality and feature modules.

• Organize directories based on feature modules, such as 'auth', 'todos', 'users'.

• Separate concerns by having directories for actions, reducers, components, and containers.

• Utilize a 'shared' directory for common functionality used across multiple feature modules.

• Consider using a 'utils' directory for utility functions and helpers.

• Keep the structure flat and avoid nesting directories t...read more

React uses a diffing algorithm called Virtual DOM to efficiently update the actual DOM.

• React creates a virtual representation of the DOM called Virtual DOM.

• When state or props change, React compares the Virtual DOM with the actual DOM to find the differences.

• React then updates only the parts of the actual DOM that have changed, minimizing re-renders and improving performance.

A higher order function is a function that takes one or more functions as arguments or returns a function as its result.

• Higher order functions can be used to create abstractions and compose functions together.

• Examples include map, filter, and reduce functions in JavaScript.

• Higher order functions can also be used for event handling and asynchronous programming.

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

• Variable declarations are hoisted to the top of their scope but not their assignments.

• Function declarations are fully hoisted, meaning they can be called before they are declared.

• Hoisting can lead to unexpected behavior if not understood properly.

Combine Reducer is a function in Redux that combines multiple reducers into a single reducer function.

• Combines multiple reducers into a single reducer function

• Helps manage different pieces of state in Redux store

• Improves code organization and maintainability

• Example: combineReducers({ reducer1, reducer2 })

• Example: const rootReducer = combineReducers({ reducer1, reducer2 })

Callbacks in JavaScript are functions passed as arguments to other functions to be executed later.

• Callbacks are commonly used in event handling, asynchronous programming, and functional programming.

• They allow for functions to be executed after another function has finished executing.

• Example: setTimeout function takes a callback function as an argument to be executed after a specified time.

Relay is a GraphQL client specifically designed for React, while Redux is a state management library for any JavaScript app.

• Relay is tightly integrated with GraphQL, providing a declarative way to fetch and manage data for React components.

• Redux is a standalone state management library that can be used with any JavaScript framework, not just React.

• Relay encourages colocating data requirements with React components, while Redux separates data fetching and state management.

• Rela...read more

Closures in JavaScript allow functions to retain access to variables from their parent scope even after the parent function has finished executing.

• Closures are created whenever a function is defined within another function.

• They allow the inner function to access variables from the outer function, even after the outer function has finished executing.

• Closures are commonly used to create private variables and functions in JavaScript.

• Example: function outerFunction() { let outerV...read more

Reconciliation in ReactJS is the process of updating the DOM to match the virtual DOM after a component's state or props have changed.

• Reconciliation is the algorithm React uses to update the DOM efficiently.

• It compares the virtual DOM with the actual DOM and only updates the parts that have changed.

• Reconciliation is a key feature that helps React achieve high performance.

• Example: When a component's state changes, React uses reconciliation to determine which parts of the DOM n...read more