ValueLabs React Developer Interview Questions and Answers

Yes, it is mandatory for Reducer to have an initial state.

• Initial state defines the starting point of the state tree.

• It helps in defining the shape of the state tree.

• It is used to set default values for the state properties.

• It is also used to reset the state to its initial values.

• Example: const initialState = { count: 0 };

• Example: const initialState = { name: '', age: 0 };

React re-renders just the part of the page that has changed, thanks to its virtual DOM.

• React uses a virtual DOM to track changes in the UI.

• When a component's state or props change, React compares the virtual DOM with the real DOM and updates only the necessary parts.

• This approach improves performance by minimizing the number of DOM manipulations.

• React's diffing algorithm efficiently determines the minimal set of c...read more

Service Workers are scripts that run in the background and can intercept network requests, cache or modify responses.

• Offline support for web applications

• Push notifications

• Background synchronization

• Reduced network usage and faster page loads

• Progressive Web Apps (PWA)

Minimum coverage for an app and code pushed to production/master branch while deployment.

• Minimum coverage for an app depends on the project requirements and complexity.

• Generally, a coverage of 80% or higher is considered good.

• Code pushed to production/master branch should be thoroughly tested and reviewed.

• Continuous integration and deployment can help automate this process.

• Examples of tools for code coverage inclu...read more

Redux-Saga is a middleware for Redux that handles side effects. Actions can be dispatched from components using mapDispatchToProps.

• Redux-Saga is used to handle side effects like API calls and asynchronous actions.

• It uses generator functions to make asynchronous code look synchronous.

• Sagas listen for specific actions and perform tasks based on those actions.

• To dispatch actions from components, use mapDispatchToProp...read more