Amazon Lab126 Interview Questions and Answers

To connect a component to Redux store, we use the connect function from the react-redux library.

• Import the connect function from react-redux.

• Use the connect function to wrap the component and connect it to the Redux store.

• The connect function takes two parameters: mapStateToProps and mapDispatchToProps.

• mapStateToProps is a function that maps the state from the Redux store to the component's props.

• mapDispatchToProps is ...read more

Context API is a way to share data between components without passing props down manually.

• Context API provides a way to pass data through the component tree without having to pass props down manually at every level.

• It is useful for sharing data that needs to be accessed by many components at different levels of the tree.

• Initial state can be set in Context API using the createContext() function.

• There is no need to have ...read more

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 };

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 include Je

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 change

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)

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 mapDispatchToProps to ...read more

Java has four pillars: Inheritance, Encapsulation, Abstraction, and Polymorphism.

• Inheritance allows a class to inherit properties and methods from another class.

• Encapsulation is the practice of hiding data and methods within a class.

• Abstraction is the process of hiding implementation details while showing only the necessary information.

• Polymorphism allows objects to take on multiple forms or behaviors.

• Example: A car cl...read more