React_Hooks v1.5.pdf: Chapter Seven. скачать в хорошем качестве

React_Hooks v1.5.pdf: Chapter Seven.

Based on the "Designing React Hooks the Right Way" documentation and general React educational resources, Chapter 7, "Use Context to Cover an Area," focuses on advanced state management, specifically managing shared data across a component tree without prop drilling. Here is a long description of the content, concepts, and applications covered in this chapter: 1. The Concept: "Area Updates" vs. Component Updates Chapter 7 introduces the concept of an "area update". While useState is great for local component state, it becomes difficult to manage when multiple, deeply nested components need access to the same data (e.g., user theme, language settings, authenticated user info). Instead of passing props down five levels ("prop drilling"), the chapter explains how to use useContext to update a specific "area" of the component tree. 2. The Solution: useContext The useContext hook is presented as the primary solution to share data with consumers without nesting. What it does: It allows a component to subscribe to React context. How it works: When a context provider updates, all component consumers that use that context automatically receive the new value and re-render. 3. Key Topics Covered Introducing React Context: Understanding how to create a context using createContext and provide it with a provider component. Understanding useContext Design: Deep dive into how useContext interacts with the React renderer to trigger updates. Test Driving useContext: Step-by-step implementation of a context hook in a real application. Practical Examples: Theme Switcher: Applying context to change the app theme globally. Data Table: Using context to manage data within a table without passing props to every row. 4. Advanced Concepts & Best Practices Context Optimization: The chapter emphasizes that when a provider updates, all consumers update. Therefore, it discusses how to keep context values lightweight to avoid unnecessary re-renders. Context Scope & Value: Techniques for scoping context so that only specific branches of the application receive updates, improving performance. Using useReducer with Context: While not the main focus, the chapter often touches upon combining useReducer and useContext for Redux-like global state management. 5. Summary of the Chapter By the end of Chapter 7, you are expected to understand: Why and when to choose useContext over useState or useReducer. How to structure context providers to avoid "prop drilling." How to properly consume context in child components. The performance implications of large context objects. In the context of the popular technical book "Designing React Hooks the Right Way" by Packt Publishing, Chapter 7, titled "Use Context to Cover an Area," focuses on using the useContext hook to manage "area updates"—state changes that affect a specific subtree of components rather than the entire application or just a single component. Key Concepts Covered in Chapter 7: Area Updates: Unlike global state which affects everything, an "area update" targets a specific section of the UI. This chapter explains how useContext is the ideal tool for sharing values within these localized scopes. The useContext Design: It provides a deep dive into the internal data structures and source code logic that allow React to propagate changes from a provider to its consumers efficiently. Eliminating Prop Drilling: The chapter demonstrates how hooks allow components to consume shared data (like themes or user profiles) without manually passing props through every intermediate level of the component tree. Practical Implementations: Theme Switching: Using context to apply styling across a nested set of UI components. Table Components: Managing shared state across complex table structures where cells and rows need access to common data. Performance Considerations: It covers "bailout" mechanisms, explaining how React prevents unnecessary re-renders when a context value remains unchanged. Summary of Chapter Objectives By the end of this chapter, readers understand how to transition from managing simple local state to architecting complex, shared state within specific UI regions. It serves as a bridge between basic hooks like useState and advanced application-wide state management. For a visual walkthrough of how these concepts come together to build efficient components: Would you like to see a code example of a useContext implementation for one of the specific scenarios mentioned, such as a theme switcher? In the book "Designing React Hooks the Right Way", Chapter 7 is titled "Use Context to Cover an Area". It provides an in-depth exploration of how to manage state across a localized group of components without manually passing props through every level. Key Concepts Covered Data. Area Updates: The chapter introduces the concept of an "area update," which refers to propagating changes to a specific section of the component tree rather than the entire application or just a single component.