工程化与框架系列（10）--微前端架构

微前端架构 🏗️

微前端是一种将前端应用分解成更小、更易管理的独立部分的架构模式。本文将详细介绍微前端的核心概念、实现方案和最佳实践。

微前端概述 🌟

💡 小知识：微前端的核心理念是将前端应用分解成一系列独立部署、松耦合的小型应用，每个应用可以由不同的团队使用不同的技术栈开发。

为什么需要微前端

在大型前端应用开发中，微前端架构能带来以下优势：

技术栈灵活性
- 支持多框架共存
- 渐进式技术迁移
- 团队技术选择自由
- 复用已有应用资产
团队自主性
- 独立开发部署
- 团队边界清晰
- 降低协作成本
- 提高开发效率
应用可维护性
- 代码库规模可控
- 模块职责单一
- 降低耦合度
- 简化测试和部署
性能优化空间
- 按需加载应用
- 独立缓存策略
- 资源并行加载
- 性能瓶颈隔离

实现方案详解 ⚡

基于路由的实现

// router-based.ts
interface MicroApp {name: string;entry: string;container: string;activeRule: string;
}export class RouterBasedMicroFrontend {private apps: MicroApp[] = [];constructor(apps: MicroApp[]) {this.apps = apps;this.initializeRouter();}private initializeRouter(): void {window.addEventListener('popstate', () => {this.handleRouteChange();});// 初始化时加载匹配的应用this.handleRouteChange();}private handleRouteChange(): void {const path = window.location.pathname;const app = this.apps.find(app => path.startsWith(app.activeRule));if (app) {this.loadApp(app);}}private async loadApp(app: MicroApp): Promise<void> {try {// 加载应用资源const html = await this.fetchAppHTML(app.entry);const container = document.querySelector(app.container);if (container) {container.innerHTML = html;this.executeAppScripts(app);}} catch (error) {console.error(`Failed to load app ${app.name}:`, error);}}private async fetchAppHTML(entry: string): Promise<string> {const response = await fetch(entry);return await response.text();}private executeAppScripts(app: MicroApp): void {// 执行应用脚本// 这里需要处理JS隔离等问题}
}// 使用示例
const microFrontend = new RouterBasedMicroFrontend([{name: 'app1',entry: 'http://localhost:3001',container: '#app1-container',activeRule: '/app1'},{name: 'app2',entry: 'http://localhost:3002',container: '#app2-container',activeRule: '/app2'}
]);

基于Web Components的实现

// web-components.ts
interface WebComponentApp {name: string;element: string;url: string;
}export class WebComponentMicroFrontend {constructor(apps: WebComponentApp[]) {this.registerApps(apps);}private registerApps(apps: WebComponentApp[]): void {apps.forEach(app => {this.defineCustomElement(app);});}private async defineCustomElement(app: WebComponentApp): Promise<void> {class MicroApp extends HTMLElement {private shadow: ShadowRoot;constructor() {super();this.shadow = this.attachShadow({ mode: 'open' });}async connectedCallback() {try {const content = await this.loadAppContent(app.url);this.shadow.innerHTML = content;await this.executeScripts();} catch (error) {console.error(`Failed to load ${app.name}:`, error);}}private async loadAppContent(url: string): Promise<string> {const response = await fetch(url);return await response.text();}private async executeScripts(): Promise<void> {// 执行应用脚本，确保在Shadow DOM上下文中运行}}customElements.define(app.element, MicroApp);}
}// 使用示例
const webComponentMicro = new WebComponentMicroFrontend([{name: 'app1',element: 'micro-app1',url: 'http://localhost:3001/app1'},{name: 'app2',element: 'micro-app2',url: 'http://localhost:3002/app2'}
]);

通信机制实现 🔄

事件总线

// event-bus.ts
type EventHandler = (data: any) => void;export class EventBus {private static instance: EventBus;private events: Map<string, EventHandler[]>;private constructor() {this.events = new Map();}public static getInstance(): EventBus {if (!EventBus.instance) {EventBus.instance = new EventBus();}return EventBus.instance;}public on(event: string, handler: EventHandler): void {if (!this.events.has(event)) {this.events.set(event, []);}this.events.get(event)!.push(handler);}public off(event: string, handler: EventHandler): void {if (!this.events.has(event)) return;const handlers = this.events.get(event)!;const index = handlers.indexOf(handler);if (index > -1) {handlers.splice(index, 1);}}public emit(event: string, data: any): void {if (!this.events.has(event)) return;this.events.get(event)!.forEach(handler => {try {handler(data);} catch (error) {console.error(`Error in event handler for ${event}:`, error);}});}
}// 使用示例
const eventBus = EventBus.getInstance();// 在应用A中订阅事件
eventBus.on('userLogin', (user) => {console.log('User logged in:', user);
});// 在应用B中触发事件
eventBus.emit('userLogin', { id: 1, name: 'John Doe' 
});

状态共享

// shared-state.ts
interface StateChangeListener<T> {(newState: T, oldState: T): void;
}export class SharedState<T extends object> {private state: T;private listeners: StateChangeListener<T>[] = [];constructor(initialState: T) {this.state = new Proxy(initialState, {set: (target, property, value) => {const oldState = { ...this.state };target[property as keyof T] = value;this.notifyListeners(this.state, oldState);return true;}});}public getState(): T {return this.state;}public setState(partial: Partial<T>): void {const oldState = { ...this.state };Object.assign(this.state, partial);this.notifyListeners(this.state, oldState);}public subscribe(listener: StateChangeListener<T>): () => void {this.listeners.push(listener);return () => {const index = this.listeners.indexOf(listener);if (index > -1) {this.listeners.splice(index, 1);}};}private notifyListeners(newState: T, oldState: T): void {this.listeners.forEach(listener => {try {listener(newState, oldState);} catch (error) {console.error('Error in state change listener:', error);}});}
}// 使用示例
interface UserState {isLoggedIn: boolean;user: {id: number;name: string;} | null;
}const sharedState = new SharedState<UserState>({isLoggedIn: false,user: null
});// 在应用A中订阅状态变化
sharedState.subscribe((newState, oldState) => {console.log('State changed:', { newState, oldState });
});// 在应用B中更新状态
sharedState.setState({isLoggedIn: true,user: {id: 1,name: 'John Doe'}
});

样式隔离方案 🎨

CSS Module Federation

// style-isolation.ts
interface StyleConfig {prefix: string;scope: string;
}export class StyleIsolation {private config: StyleConfig;constructor(config: StyleConfig) {this.config = config;this.initializeStyleIsolation();}private initializeStyleIsolation(): void {// 添加样式作用域document.documentElement.setAttribute('data-app-scope',this.config.scope);// 处理动态添加的样式this.observeStyleChanges();}private observeStyleChanges(): void {const observer = new MutationObserver((mutations) => {mutations.forEach(mutation => {mutation.addedNodes.forEach(node => {if (node instanceof HTMLStyleElement) {this.processStyle(node);}});});});observer.observe(document.head, {childList: true});}private processStyle(styleElement: HTMLStyleElement): void {const css = styleElement.textContent || '';const scopedCss = this.scopeCSS(css);styleElement.textContent = scopedCss;}private scopeCSS(css: string): string {// 为所有选择器添加作用域前缀return css.replace(/([^}]*){/g, (match) => {return match.split(',').map(selector => `[data-app-scope="${this.config.scope}"] ${selector.trim()}`).join(',');});}
}// 使用示例
const styleIsolation = new StyleIsolation({prefix: 'app1',scope: 'micro-app1'
});

性能优化策略 ⚡

资源加载优化

// resource-loader.ts
interface ResourceConfig {js: string[];css: string[];prefetch?: string[];
}export class ResourceLoader {private loadedResources: Set<string> = new Set();private loading: Map<string, Promise<void>> = new Map();public async loadApp(config: ResourceConfig): Promise<void> {try {// 并行加载JS和CSS资源await Promise.all([this.loadJSResources(config.js),this.loadCSSResources(config.css)]);// 预加载其他资源if (config.prefetch) {this.prefetchResources(config.prefetch);}} catch (error) {console.error('Failed to load resources:', error);throw error;}}private async loadJSResources(urls: string[]): Promise<void> {const promises = urls.map(url => this.loadJS(url));await Promise.all(promises);}private async loadCSSResources(urls: string[]): Promise<void> {const promises = urls.map(url => this.loadCSS(url));await Promise.all(promises);}private async loadJS(url: string): Promise<void> {if (this.loadedResources.has(url)) {return;}if (this.loading.has(url)) {return this.loading.get(url);}const promise = new Promise<void>((resolve, reject) => {const script = document.createElement('script');script.src = url;script.async = true;script.onload = () => {this.loadedResources.add(url);this.loading.delete(url);resolve();};script.onerror = () => {this.loading.delete(url);reject(new Error(`Failed to load script: ${url}`));};document.head.appendChild(script);});this.loading.set(url, promise);return promise;}private async loadCSS(url: string): Promise<void> {if (this.loadedResources.has(url)) {return;}return new Promise((resolve, reject) => {const link = document.createElement('link');link.rel = 'stylesheet';link.href = url;link.onload = () => {this.loadedResources.add(url);resolve();};link.onerror = () => {reject(new Error(`Failed to load CSS: ${url}`));};document.head.appendChild(link);});}private prefetchResources(urls: string[]): void {urls.forEach(url => {if (!this.loadedResources.has(url)) {const link = document.createElement('link');link.rel = 'prefetch';link.href = url;document.head.appendChild(link);}});}
}

最佳实践建议 ⭐

应用设计原则

独立性原则
- 应用间松耦合
- 独立开发部署
- 运行时隔离
- 故障隔离
统一规范
- 通信协议标准
- 路由管理规范
- 样式命名规范
- 错误处理机制
性能优化
- 按需加载策略
- 资源复用机制
- 缓存优化方案
- 预加载策略

开发流程建议

项目初始化

# 创建微前端项目结构
mkdir micro-frontend && cd micro-frontend
mkdir container app1 app2 shared# 初始化基座应用
cd container
npm init -y
npm install @micro-frontend/core# 初始化子应用
cd ../app1
npm init -y
npm install @micro-frontend/app

开发规范

// 子应用生命周期规范
interface MicroAppLifecycle {bootstrap(): Promise<void>;mount(props: Record<string, any>): Promise<void>;unmount(): Promise<void>;
}// 实现示例
export class MicroApp implements MicroAppLifecycle {async bootstrap(): Promise<void> {// 应用初始化}async mount(props: Record<string, any>): Promise<void> {// 应用挂载}async unmount(): Promise<void> {// 应用卸载}
}