掌握 React：你應該永遠知道的基本事情-js教程-PHP中文網

Mastering React: Essential Things You Should Always Know

React 已成為建立使用者介面最受歡迎的 JavaScript 函式庫之一。無論您是初學者還是中級開發人員，都有幾個關鍵概念和最佳實踐可以提高您的 React 技能。讓我們深入探討使用 React 時應始終了解的基本知識。

1. 組件組成和復用性

React 的基本優勢在於其強大的基於元件的架構，該架構非常重視小型、可重複使用元件的開發和創建。這種方法不僅提高了建立使用者介面的效率，還鼓勵在整個應用程式的多個位置使用這些元件，從而提高一致性並減少程式碼冗餘。

// Bad: Monolithic Component
function UserProfile() {
  return (
    <div>
      <h1>{user.name}</h1>
      <div>{user.bio}</div>
      <button onClick={handleEdit}>Edit Profile</button>
      <div>
        <h2>User Posts</h2>
        {user.posts.map(post => (
          <div key={post.id}>{post.content}</div>
        ))}
      </div>
    </div>
  );
}

// Good: Composable Components
function UserHeader({ name }) {
  return <h1>{name}</h1>;
}

function UserBio({ bio }) {
  return <div>{bio}</div>;
}

function UserPosts({ posts }) {
  return (
    <div>
      <h2>User Posts</h2>
      {posts.map(post => (
        <PostCard key={post.id} post={post} />
      ))}
    </div>
  );
}

function UserProfile({ user }) {
  return (
    <div>
      <UserHeader name={user.name} />
      <UserBio bio={user.bio} />
      <EditProfileButton userId={user.id} />
      <UserPosts posts={user.posts} />
    </div>
  );
}

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2. 狀態管理策略

了解在應用程式開發過程中使用本機狀態、上下文和各種狀態管理程式庫的適當時機非常重要。認識到何時有效地使用這些工具可以大大增強程式碼的組織和功能。

import React, { useState, useContext, useReducer } from 'react';

// Local State (for simple, component-specific state)
function Counter() {
  const [count, setCount] = useState(0);
  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={() => setCount(count + 1)}>Increment</button>
    </div>
  );
}

// Context API (for medium-complexity state sharing)
const ThemeContext = React.createContext();

function ThemeProvider({ children }) {
  const [theme, setTheme] = useState('light');

  return (
    <ThemeContext.Provider value={{ theme, setTheme }}>
      {children}
    </ThemeContext.Provider>
  );
}

// Reducer for Complex State Management
function userReducer(state, action) {
  switch (action.type) {
    case 'LOGIN':
      return { ...state, isAuthenticated: true, user: action.payload };
    case 'LOGOUT':
      return { ...state, isAuthenticated: false, user: null };
    default:
      return state;
  }
}

function AuthComponent() {
  const [state, dispatch] = useReducer(userReducer, {
    isAuthenticated: false,
    user: null
  });

  const login = (userData) => {
    dispatch({ type: 'LOGIN', payload: userData });
  };

  const logout = () => {
    dispatch({ type: 'LOGOUT' });
  };
}

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3. 效能優化技術

永遠注意性能：

import React, { useMemo, useCallback, memo } from 'react';

// Memoization to prevent unnecessary re-renders
const ExpensiveComponent = memo(({ data }) => {
  // Render logic
});

function ParentComponent({ data }) {
  // useMemo for expensive calculations
  const processedData = useMemo(() => {
    return data.map(item => heavyProcessing(item));
  }, [data]);

  // useCallback to memoize event handlers
  const handleClick = useCallback(() => {
    // Click handler logic
  }, []);

  return (
    <div>
      <ExpensiveComponent data={processedData} />
      <button onClick={handleClick}>Perform Action</button>
    </div>
  );
}

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4. 錯誤處理與邊界

實現錯誤邊界以優雅地處理運行時錯誤：

class ErrorBoundary extends React.Component {
  constructor(props) {
    super(props);
    this.state = { hasError: false };
  }

  static getDerivedStateFromError(error) {
    return { hasError: true };
  }

  componentDidCatch(error, errorInfo) {
    // Log error to monitoring service
    logErrorToService(error, errorInfo);
  }

  render() {
    if (this.state.hasError) {
      return <h1>Something went wrong.</h1>;
    }

    return this.props.children;
  }
}

function App() {
  return (
    <ErrorBoundary>
      <MainApplication />
    </ErrorBoundary>
  );
}

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5. Hook 最佳實踐

使用自訂鉤子擷取和共用狀態邏輯
遵循 Hooks 規則（僅在頂層呼叫 hooks）
避免將鉤子放入條件或循環內

// Custom Hook Example
function useLocalStorage(key, initialValue) {
  const [storedValue, setStoredValue] = useState(() => {
    try {
      const item = window.localStorage.getItem(key);
      return item ? JSON.parse(item) : initialValue;
    } catch (error) {
      console.log(error);
      return initialValue;
    }
  });

  const setValue = (value) => {
    try {
      const valueToStore = value instanceof Function 
        ? value(storedValue) 
        : value;
      setStoredValue(valueToStore);
      window.localStorage.setItem(key, JSON.stringify(valueToStore));
    } catch (error) {
      console.log(error);
    }
  };

  return [storedValue, setValue];
}

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