The ability of Immutable.js to use previous data structures to efficiently create new ones without deep cloning is referred to as "Structural Sharing." This core concept of Immutable.js helps optimize memory usage and performance by reusing parts of the existing data structures when creating new ones. Instead of copying everything, it shares common elements, which is key to Immutable.js's efficiency and immutability.

Redux follows several core principles, including immutable state, a single source of truth, and changes made through pure functions (reducers). Asynchronous actions, while commonly used with Redux, are not a core principle of Redux itself. They are more of a common practice when handling asynchronous operations in Redux applications.

Error boundaries in React do not catch errors inside child components. When an error occurs in a child component, React will propagate it to the nearest error boundary in the component hierarchy. This is important for isolating and handling errors effectively.

The main responsibility of an action in Redux is to modify the state in reducers. Actions are plain JavaScript objects that describe changes to the application's state. They carry information about what happened (the action type) and any additional data needed to update the state. Reducers then interpret these actions and apply the state changes accordingly. Actions don't handle UI rendering, layout, or database queries; their focus is on state management.

In Jest, when you want to mock a specific function implementation, you would use the mockImplementation method on the mock. This allows you to define custom behavior for the mocked function, such as returning specific values or throwing errors. The other options are not the correct method for this purpose in Jest.

Service workers contribute to making a web application work offline by caching web application resources for offline use. Service workers act as a proxy between the web application and the network, intercepting and caching requests. When the user goes offline, the service worker can serve cached content, allowing the web app to continue functioning and providing a seamless offline experience.

In the React community, a common naming convention for Higher Order Components (HOCs) is to prefix them with "with" followed by the component name they enhance. This convention helps developers identify HOCs and understand their purpose in enhancing components. The other naming conventions mentioned in options 1, 2, and 4 are not as commonly used in the React community for HOCs.

In this scenario, you can utilize React.memo to optimize the component's re-renders. React.memo is a higher-order component (HOC) that memoizes a component, preventing it from re-rendering when its props remain unchanged. React DevTools can help you identify the problem, but React.memo is the method to prevent unnecessary re-renders.

The TypeScript keyword used to create a type that can be one of several types is called union. Unions are used to specify that a value can have one of several possible types. This is valuable for scenarios where a variable or property can accept multiple data types. The other options (any, object, function) do not specifically define a type that can be one of several types.

The Proxy Pattern can help flatten the component tree while still sharing the logic. It allows you to control access to an object by creating a surrogate or placeholder for it. In the context of React or similar frameworks, a proxy component can be used to encapsulate complex logic, making the component tree shallower and more maintainable. The other patterns listed do not directly address this issue.