JavaScript系列（25）--性能优化技术详解

JavaScript性能优化技术详解 ⚡

今天，让我们深入探讨JavaScript的性能优化技术。掌握这些技术对于构建高性能的JavaScript应用至关重要。

性能优化基础 🌟

💡 小知识：JavaScript性能优化涉及多个方面，包括代码执行效率、内存使用、网络请求、渲染性能等。通过合理的优化策略，我们可以显著提升应用的响应速度和用户体验。

代码执行优化 📊

// 1. 循环优化
function loopOptimization() {const arr = new Array(1000000).fill(1);// 不好的做法for (let i = 0; i < arr.length; i++) {// 每次都要获取数组长度}// 好的做法for (let i = 0, len = arr.length; i < len; i++) {// 缓存数组长度}// 更好的做法arr.forEach(item => {// 使用原生方法});// 最好的做法（特定场景）const typedArr = new Float64Array(1000000);// 使用类型化数组提升性能
}// 2. 函数优化
class FunctionOptimizer {// 函数记忆化static memoize(fn) {const cache = new Map();return (...args) => {const key = JSON.stringify(args);if (cache.has(key)) {return cache.get(key);}const result = fn.apply(this, args);cache.set(key, result);return result;};}// 函数去抖static debounce(fn, delay) {let timeoutId;return function(...args) {clearTimeout(timeoutId);timeoutId = setTimeout(() => fn.apply(this, args), delay);};}// 函数节流static throttle(fn, limit) {let inThrottle;return function(...args) {if (!inThrottle) {fn.apply(this, args);inThrottle = true;setTimeout(() => inThrottle = false, limit);}};}
}// 3. 数据结构优化
class DataStructureOptimizer {// Map vs Object性能比较static mapVsObject() {const map = new Map();const obj = {};const iterations = 1000000;console.time('Map');for (let i = 0; i < iterations; i++) {map.set(i, i);map.get(i);}console.timeEnd('Map');console.time('Object');for (let i = 0; i < iterations; i++) {obj[i] = i;obj[i];}console.timeEnd('Object');}// Set vs Array性能比较static setVsArray() {const set = new Set();const arr = [];const iterations = 1000000;console.time('Set');for (let i = 0; i < iterations; i++) {set.add(i);set.has(i);}console.timeEnd('Set');console.time('Array');for (let i = 0; i < iterations; i++) {arr.push(i);arr.includes(i);}console.timeEnd('Array');}
}

内存优化技术 🚀

// 1. 对象池实现
class ObjectPool {constructor(factory, initialSize = 10) {this.factory = factory;this.pool = [];this.init(initialSize);}init(size) {for (let i = 0; i < size; i++) {this.pool.push(this.factory());}}acquire() {return this.pool.length > 0 ? this.pool.pop() : this.factory();}release(obj) {if (this.pool.length < this.maxSize) {if (obj.reset) obj.reset();this.pool.push(obj);}}
}// 2. 内存泄漏防护
class MemoryLeakGuard {constructor() {this.observers = new WeakSet();this.eventHandlers = new WeakMap();}observe(target) {if (!this.observers.has(target)) {this.observers.add(target);this.eventHandlers.set(target, new Map());}}addHandler(target, event, handler) {if (this.eventHandlers.has(target)) {const handlers = this.eventHandlers.get(target);handlers.set(event, handler);target.addEventListener(event, handler);}}removeHandler(target, event) {if (this.eventHandlers.has(target)) {const handlers = this.eventHandlers.get(target);const handler = handlers.get(event);if (handler) {target.removeEventListener(event, handler);handlers.delete(event);}}}cleanup(target) {if (this.eventHandlers.has(target)) {const handlers = this.eventHandlers.get(target);handlers.forEach((handler, event) => {target.removeEventListener(event, handler);});this.eventHandlers.delete(target);this.observers.delete(target);}}
}// 3. 大数据处理优化
class BigDataProcessor {// 分片处理static async processInChunks(items, chunkSize, processor) {const results = [];for (let i = 0; i < items.length; i += chunkSize) {const chunk = items.slice(i, i + chunkSize);const chunkResults = await Promise.all(chunk.map(item => processor(item)));results.push(...chunkResults);// 让出主线程await new Promise(resolve => setTimeout(resolve, 0));}return results;}// 虚拟列表实现static createVirtualList(container, items, rowHeight) {let scrollTop = 0;let visibleItems = [];function updateVisibleItems() {const containerHeight = container.clientHeight;const startIndex = Math.floor(scrollTop / rowHeight);const endIndex = Math.min(startIndex + Math.ceil(containerHeight / rowHeight),items.length);visibleItems = items.slice(startIndex, endIndex).map((item, index) => ({...item,style: {position: 'absolute',top: (startIndex + index) * rowHeight + 'px',height: rowHeight + 'px'}}));render();}function render() {container.innerHTML = '';visibleItems.forEach(item => {const element = document.createElement('div');Object.assign(element.style, item.style);element.textContent = item.content;container.appendChild(element);});}container.style.height = items.length * rowHeight + 'px';container.style.position = 'relative';container.style.overflow = 'auto';container.addEventListener('scroll', () => {scrollTop = container.scrollTop;updateVisibleItems();});updateVisibleItems();}
}

网络优化策略 🌐

// 1. 请求优化
class RequestOptimizer {constructor() {this.cache = new Map();this.pendingRequests = new Map();}// 请求去重async request(url, options = {}) {const key = `${url}-${JSON.stringify(options)}`;// 检查缓存if (this.cache.has(key)) {return this.cache.get(key);}// 检查是否有相同的请求正在进行if (this.pendingRequests.has(key)) {return this.pendingRequests.get(key);}// 发起新请求const promise = fetch(url, options).then(response => response.json()).finally(() => {this.pendingRequests.delete(key);});this.pendingRequests.set(key, promise);const result = await promise;this.cache.set(key, result);return result;}// 批量请求async batchRequest(urls, options = {}) {return Promise.all(urls.map(url => this.request(url, options)));}
}// 2. 资源预加载
class ResourcePreloader {constructor() {this.loaded = new Set();}preloadImage(url) {if (this.loaded.has(url)) return Promise.resolve();return new Promise((resolve, reject) => {const img = new Image();img.onload = () => {this.loaded.add(url);resolve();};img.onerror = reject;img.src = url;});}preloadScript(url) {if (this.loaded.has(url)) return Promise.resolve();return new Promise((resolve, reject) => {const script = document.createElement('script');script.onload = () => {this.loaded.add(url);resolve();};script.onerror = reject;script.src = url;document.head.appendChild(script);});}preloadStyle(url) {if (this.loaded.has(url)) return Promise.resolve();return new Promise((resolve, reject) => {const link = document.createElement('link');link.rel = 'stylesheet';link.onload = () => {this.loaded.add(url);resolve();};link.onerror = reject;link.href = url;document.head.appendChild(link);});}
}// 3. 数据缓存策略
class CacheStrategy {constructor(storage = localStorage) {this.storage = storage;this.prefix = 'cache_';}set(key, value, ttl = 3600000) { // 默认1小时const item = {value,timestamp: Date.now(),ttl};this.storage.setItem(this.prefix + key,JSON.stringify(item));}get(key) {const item = JSON.parse(this.storage.getItem(this.prefix + key));if (!item) return null;if (Date.now() - item.timestamp > item.ttl) {this.storage.removeItem(this.prefix + key);return null;}return item.value;}clear() {Object.keys(this.storage).filter(key => key.startsWith(this.prefix)).forEach(key => this.storage.removeItem(key));}
}

渲染性能优化 🎨

// 1. DOM操作优化
class DOMOptimizer {// 批量DOM更新static batchUpdate(elements, updates) {const fragment = document.createDocumentFragment();elements.forEach(element => {const clone = element.cloneNode(true);updates(clone);fragment.appendChild(clone);});elements[0].parentNode.replaceChildren(fragment);}// 虚拟DOM实现static createVirtualDOM(element) {return {type: element.tagName.toLowerCase(),props: Array.from(element.attributes).reduce((props, attr) => {props[attr.name] = attr.value;return props;}, {}),children: Array.from(element.childNodes).map(node => {if (node.nodeType === 3) return node.textContent;return this.createVirtualDOM(node);})};}// 最小化重排重绘static optimizeReflow(element, updates) {const originalDisplay = element.style.display;element.style.display = 'none';updates(element);element.style.display = originalDisplay;}
}// 2. 动画性能优化
class AnimationOptimizer {constructor() {this.animations = new Map();}// 使用requestAnimationFrameanimate(element, properties, duration) {const startTime = performance.now();const initialValues = {};Object.keys(properties).forEach(prop => {initialValues[prop] = parseFloat(getComputedStyle(element)[prop]);});const animation = timestamp => {const progress = (timestamp - startTime) / duration;if (progress < 1) {Object.keys(properties).forEach(prop => {const initial = initialValues[prop];const target = properties[prop];const current = initial + (target - initial) * progress;element.style[prop] = current + 'px';});this.animations.set(element,requestAnimationFrame(animation));} else {Object.keys(properties).forEach(prop => {element.style[prop] = properties[prop] + 'px';});this.animations.delete(element);}};this.animations.set(element,requestAnimationFrame(animation));}// 停止动画stop(element) {if (this.animations.has(element)) {cancelAnimationFrame(this.animations.get(element));this.animations.delete(element);}}
}// 3. 图片优化
class ImageOptimizer {// 图片懒加载static lazyLoad(images) {const observer = new IntersectionObserver((entries, observer) => {entries.forEach(entry => {if (entry.isIntersecting) {const img = entry.target;img.src = img.dataset.src;observer.unobserve(img);}});});images.forEach(img => observer.observe(img));}// 图片预加载static preload(urls) {return Promise.all(urls.map(url => {return new Promise((resolve, reject) => {const img = new Image();img.onload = resolve;img.onerror = reject;img.src = url;});}));}// 响应式图片static createResponsiveImage(url, sizes) {const img = document.createElement('img');img.srcset = sizes.map(size => `${url}-${size}w.jpg ${size}w`).join(', ');img.sizes = '(max-width: 768px) 100vw, 50vw';return img;}
}

最佳实践建议 💡

性能监控

// 1. 性能监控工具
class PerformanceMonitor {constructor() {this.metrics = new Map();}// 测量执行时间measure(name, fn) {const start = performance.now();const result = fn();const duration = performance.now() - start;this.metrics.set(name, {duration,timestamp: Date.now()});return result;}// 异步操作测量async measureAsync(name, fn) {const start = performance.now();const result = await fn();const duration = performance.now() - start;this.metrics.set(name, {duration,timestamp: Date.now()});return result;}// 获取性能报告getReport() {return Array.from(this.metrics.entries()).map(([name, data]) => ({name,duration: data.duration,timestamp: new Date(data.timestamp).toISOString()}));}
}// 2. 性能优化检查清单
class PerformanceChecker {static checkDOMSize() {return document.querySelectorAll('*').length;}static checkEventListeners() {const elements = document.querySelectorAll('*');let count = 0;elements.forEach(element => {const listeners = getEventListeners(element);count += Object.keys(listeners).reduce((sum, type) => sum + listeners[type].length,0);});return count;}static checkMemoryUsage() {if (performance.memory) {return {usedJSHeapSize: performance.memory.usedJSHeapSize,totalJSHeapSize: performance.memory.totalJSHeapSize};}return null;}
}