Virtusa Software Services Interview Questions and Answers

Export types in ReactJS allow components, functions, and variables to be accessed and used in other files.

• Exporting a component allows it to be imported and used in other files

• Exporting a function allows it to be imported and used in other files

• Exporting a variable allows it to be imported and used in other files

Hooks are functions that allow you to use state and other React features without writing a class.

• useState is a hook that allows you to add state to functional components.

• useEffect is a hook that allows you to perform side effects in functional components.

• Hooks can only be used in functional components.

• Hooks must be called at the top level of a functional component.

• Hooks can be used to replace lifecycle methods in class...read more

The 'this' keyword in JS refers to the object that is currently executing the code.

• The value of 'this' depends on how a function is called.

• In a method, 'this' refers to the object that the method belongs to.

• In a regular function, 'this' refers to the global object (window in a browser).

• In an event handler, 'this' refers to the element that triggered the event.

• The value of 'this' can be explicitly set using call(), appl...read more

setState is a method used in React to update the state of a component.

• setState is asynchronous and batched for performance optimization.

• It merges the new state with the previous state.

• It schedules a re-render of the component and its children.

• Passing a function to setState ensures the previous state is used correctly.

• Example: this.setState({ count: this.state.count + 1 })

Answer to a React Developer interview question about class and functional components and passing props.

• Class component: class MyComponent extends React.Component {}

• Functional component: const MyComponent = (props) => {}

• Passing props from parent to child:

Promises are a way to handle asynchronous operations in JavaScript. Promise.all is used to execute multiple promises concurrently.

• Promises represent a value that may not be available yet

• They have three states: pending, fulfilled, and rejected

• Promise.all takes an array of promises and returns a new promise that resolves when all promises in the array have resolved

• If any promise in the array is rejected, the returned pro...read more

ES6 features: Spread Operator, Rest Parameter, Object Destructuring

• Spread Operator: allows an iterable to be expanded into individual elements

• Rest Parameter: allows a function to accept an indefinite number of arguments as an array

• Object Destructuring: allows extracting properties from an object and assigning them to variables