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JavaScript系列（41）--状态管理实现详解

article 2025/3/1 12:36:57

JavaScript状态管理实现详解 🔄

今天，让我们深入探讨JavaScript的状态管理实现。状态管理是现代前端应用中的核心概念，它帮助我们有效地管理和同步应用数据。

状态管理基础概念 🌟

💡 小知识：状态管理是一种用于管理应用程序数据流的模式，它通过集中式存储和单向数据流来保持数据的一致性和可预测性。

基本实现 📊

// 1. 简单的状态存储
class SimpleStore {
    constructor(initialState = {}) {
        this.state = initialState;
        this.listeners = new Set();
    }
    
    getState() {
        return this.state;
    }
    
    setState(newState) {
        this.state = { ...this.state, ...newState };
        this.notify();
    }
    
    subscribe(listener) {
        this.listeners.add(listener);
        return () => this.listeners.delete(listener);
    }
    
    notify() {
        this.listeners.forEach(listener => listener(this.state));
    }
}

// 2. 支持Action的Store
class ActionStore {
    constructor(reducer, initialState = {}) {
        this.reducer = reducer;
        this.state = initialState;
        this.listeners = new Set();
    }
    
    dispatch(action) {
        this.state = this.reducer(this.state, action);
        this.notify();
    }
    
    getState() {
        return this.state;
    }
    
    subscribe(listener) {
        this.listeners.add(listener);
        return () => this.listeners.delete(listener);
    }
    
    notify() {
        this.listeners.forEach(listener => listener(this.state));
    }
}

// 3. 状态选择器
class StoreSelector {
    constructor(store) {
        this.store = store;
        this.selectors = new Map();
        this.cache = new Map();
        
        store.subscribe(() => this.updateSelectors());
    }
    
    addSelector(key, selectorFn) {
        this.selectors.set(key, selectorFn);
        this.updateSelector(key);
    }
    
    select(key) {
        return this.cache.get(key);
    }
    
    updateSelectors() {
        this.selectors.forEach((_, key) => this.updateSelector(key));
    }
    
    updateSelector(key) {
        const selector = this.selectors.get(key);
        const state = this.store.getState();
        const newValue = selector(state);
        
        if (!this.cache.has(key) || !this.shallowEqual(this.cache.get(key), newValue)) {
            this.cache.set(key, newValue);
        }
    }
    
    shallowEqual(obj1, obj2) {
        if (obj1 === obj2) return true;
        if (!obj1 || !obj2) return false;
        return Object.keys(obj1).every(key => obj1[key] === obj2[key]);
    }
}

高级功能实现 🚀

// 1. 中间件系统
class MiddlewareStore {
    constructor(reducer, initialState = {}) {
        this.reducer = reducer;
        this.state = initialState;
        this.listeners = new Set();
        this.middlewares = [];
    }
    
    use(middleware) {
        this.middlewares.push(middleware);
    }
    
    dispatch(action) {
        const middlewareAPI = {
            getState: () => this.state,
            dispatch: (action) => this.dispatch(action)
        };
        
        const chain = this.middlewares.map(middleware => 
            middleware(middlewareAPI)
        );
        
        const composedDispatch = this.compose(...chain)(
            this.baseDispatch.bind(this)
        );
        
        composedDispatch(action);
    }
    
    baseDispatch(action) {
        this.state = this.reducer(this.state, action);
        this.notify();
    }
    
    compose(...funcs) {
        if (funcs.length === 0) return arg => arg;
        if (funcs.length === 1) return funcs[0];
        
        return funcs.reduce((a, b) => (...args) => a(b(...args)));
    }
    
    // ... 其他基本方法同ActionStore
}

// 2. 时间旅行调试器
class TimeTravel {
    constructor(store) {
        this.store = store;
        this.history = [{ state: store.getState(), action: '@@INIT' }];
        this.currentIndex = 0;
        
        store.subscribe(() => {
            if (this.isTimeTraveling) return;
            
            this.history = this.history.slice(0, this.currentIndex + 1);
            this.history.push({
                state: store.getState(),
                action: this.lastAction
            });
            this.currentIndex = this.history.length - 1;
        });
    }
    
    recordAction(action) {
        this.lastAction = action;
    }
    
    undo() {
        if (this.currentIndex > 0) {
            this.isTimeTraveling = true;
            this.currentIndex--;
            this.store.setState(this.history[this.currentIndex].state);
            this.isTimeTraveling = false;
        }
    }
    
    redo() {
        if (this.currentIndex < this.history.length - 1) {
            this.isTimeTraveling = true;
            this.currentIndex++;
            this.store.setState(this.history[this.currentIndex].state);
            this.isTimeTraveling = false;
        }
    }
    
    getHistory() {
        return this.history;
    }
    
    jumpTo(index) {
        if (index >= 0 && index < this.history.length) {
            this.isTimeTraveling = true;
            this.currentIndex = index;
            this.store.setState(this.history[index].state);
            this.isTimeTraveling = false;
        }
    }
}

// 3. 状态持久化
class PersistentStore {
    constructor(store, options = {}) {
        this.store = store;
        this.options = {
            key: 'app_state',
            storage: localStorage,
            serialize: JSON.stringify,
            deserialize: JSON.parse,
            ...options
        };
        
        this.init();
    }
    
    init() {
        // 加载持久化的状态
        const savedState = this.options.storage.getItem(this.options.key);
        if (savedState) {
            try {
                const state = this.options.deserialize(savedState);
                this.store.setState(state);
            } catch (error) {
                console.error('Failed to load persisted state:', error);
            }
        }
        
        // 订阅状态变化
        this.store.subscribe(() => this.persist());
    }
    
    persist() {
        try {
            const state = this.store.getState();
            const serialized = this.options.serialize(state);
            this.options.storage.setItem(this.options.key, serialized);
        } catch (error) {
            console.error('Failed to persist state:', error);
        }
    }
    
    clear() {
        this.options.storage.removeItem(this.options.key);
    }
}

性能优化技巧 ⚡

// 1. 批量更新优化
class BatchUpdateStore {
    constructor(initialState = {}) {
        this.state = initialState;
        this.listeners = new Set();
        this.pendingUpdates = new Map();
        this.isUpdating = false;
    }
    
    setState(key, value) {
        this.pendingUpdates.set(key, value);
        this.scheduleBatchUpdate();
    }
    
    scheduleBatchUpdate() {
        if (!this.isUpdating) {
            this.isUpdating = true;
            Promise.resolve().then(() => this.processBatchUpdate());
        }
    }
    
    processBatchUpdate() {
        const newState = { ...this.state };
        this.pendingUpdates.forEach((value, key) => {
            newState[key] = value;
        });
        
        this.state = newState;
        this.pendingUpdates.clear();
        this.isUpdating = false;
        this.notify();
    }
}

// 2. 选择器优化
class MemoizedSelector {
    constructor() {
        this.cache = new Map();
        this.lastArgs = new Map();
    }
    
    createSelector(dependencies, combiner) {
        return (...args) => {
            const key = JSON.stringify(args);
            const depValues = dependencies.map(dep => dep(...args));
            
            // 检查依赖是否改变
            if (this.shouldUpdate(key, depValues)) {
                const result = combiner(...depValues);
                this.cache.set(key, result);
                this.lastArgs.set(key, depValues);
            }
            
            return this.cache.get(key);
        };
    }
    
    shouldUpdate(key, newArgs) {
        if (!this.cache.has(key)) return true;
        
        const lastArgs = this.lastArgs.get(key);
        return !lastArgs || !this.shallowEqual(lastArgs, newArgs);
    }
    
    shallowEqual(arr1, arr2) {
        return arr1.length === arr2.length &&
               arr1.every((item, index) => item === arr2[index]);
    }
}

// 3. 状态分片
class SlicedStore {
    constructor() {
        this.slices = new Map();
        this.listeners = new Map();
    }
    
    createSlice(name, reducer, initialState) {
        if (this.slices.has(name)) {
            throw new Error(`Slice ${name} already exists`);
        }
        
        this.slices.set(name, {
            state: initialState,
            reducer
        });
        
        this.listeners.set(name, new Set());
    }
    
    dispatch(sliceName, action) {
        const slice = this.slices.get(sliceName);
        if (!slice) {
            throw new Error(`Slice ${sliceName} not found`);
        }
        
        const newState = slice.reducer(slice.state, action);
        if (newState !== slice.state) {
            slice.state = newState;
            this.notifySliceListeners(sliceName);
        }
    }
    
    subscribe(sliceName, listener) {
        const listeners = this.listeners.get(sliceName);
        if (!listeners) {
            throw new Error(`Slice ${sliceName} not found`);
        }
        
        listeners.add(listener);
        return () => listeners.delete(listener);
    }
    
    notifySliceListeners(sliceName) {
        const listeners = this.listeners.get(sliceName);
        const state = this.slices.get(sliceName).state;
        listeners.forEach(listener => listener(state));
    }
}

最佳实践建议 💡

  1. 状态设计模式
// 1. 状态隔离
class IsolatedStore {
    constructor() {
        this.stores = new Map();
    }
    
    createStore(name, initialState) {
        if (this.stores.has(name)) {
            throw new Error(`Store ${name} already exists`);
        }
        
        const store = new SimpleStore(initialState);
        this.stores.set(name, store);
        return store;
    }
    
    getStore(name) {
        const store = this.stores.get(name);
        if (!store) {
            throw new Error(`Store ${name} not found`);
        }
        return store;
    }
}

// 2. 状态同步
class SyncedStore {
    constructor(stores) {
        this.stores = stores;
        this.syncListeners = new Map();
    }
    
    sync(sourceStore, targetStore, mapper) {
        const unsubscribe = sourceStore.subscribe(state => {
            const mappedState = mapper(state);
            targetStore.setState(mappedState);
        });
        
        this.syncListeners.set(
            `${sourceStore.name}-${targetStore.name}`,
            unsubscribe
        );
    }
    
    unsync(sourceStore, targetStore) {
        const key = `${sourceStore.name}-${targetStore.name}`;
        const unsubscribe = this.syncListeners.get(key);
        if (unsubscribe) {
            unsubscribe();
            this.syncListeners.delete(key);
        }
    }
}

// 3. 状态验证
class ValidatedStore {
    constructor(schema) {
        this.schema = schema;
        this.store = new SimpleStore();
    }
    
    setState(newState) {
        const validationResult = this.validateState(newState);
        if (validationResult.isValid) {
            this.store.setState(newState);
        } else {
            throw new Error(
                `Invalid state: ${validationResult.errors.join(', ')}`
            );
        }
    }
    
    validateState(state) {
        const errors = [];
        let isValid = true;
        
        Object.entries(this.schema).forEach(([key, validator]) => {
            if (!validator(state[key])) {
                isValid = false;
                errors.push(`Invalid value for ${key}`);
            }
        });
        
        return { isValid, errors };
    }
}

结语 📝

状态管理是现代JavaScript应用中的核心概念，通过本文，我们学习了：

  1. 状态管理的基本概念和实现
  2. 高级功能如中间件和时间旅行
  3. 性能优化技巧
  4. 最佳实践和设计模式
  5. 状态验证和同步策略

💡 学习建议：在实践中，要根据应用的规模和复杂度选择合适的状态管理方案。对于小型应用，简单的状态存储就足够了；对于大型应用，则需要考虑使用更完整的状态管理解决方案。

如果你觉得这篇文章有帮助，欢迎点赞收藏，也期待在评论区看到你的想法和建议！👇

终身学习，共同成长。

咱们下一期见

💻


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