SEO优化必看！JavaScript代码优化7大技巧，让你的网站在百度搜索中快速起飞

<!-- 优化前 -->
<script src="all.js"></script>

<!-- 优化后 -->
<style>
/* 提前加载关键CSS */
.critical-css {
  display: none;
}
.critical-css-loaded {
  display: block !important;
}
</style>
<script>
document.addEventListener('DOMContentLoaded', function() {
  var style = document.createElement('link');
  style.href = 'critical.css';
  style.rel = 'stylesheet';
  styledia = 'screen';
  document.head.appendChild(style);
  document.body.classList.add('critical-css-loaded');
});
</script>
<script src="non-critical.js"></script>

// 优化前
const script = document.createElement('script');
script.src = 'https://cdn.example/script.min.js';
document.body.appendChild(script);

// 优化后（预加载）
const script = document.createElement('script');
script.src = 'https://cdn.example/script.min.js';
script.async = true;
scriptcrossOrigin = 'anonymous';
document.head.appendChild(script);

// 添加预加载标签
<link rel="preload" href="https://cdn.example/script.min.js" as="script">

// 优化前（普通AJAX）
$.ajax({
  url: 'https://api.example/data',
  success: function(data) { ... }
});

// 优化后（JSONP）
<script src="https://api.example/data?callback=handleData"></script>
<script>
function handleData(data) {
  // 处理返回数据
}
</script>

// 优化前
let timeoutId;
function delayedAction() {
  timeoutId = setTimeout(() => { /* 操作 */ }, 3000);
}

// 优化后（正确清理）
function delayedAction() {
  timeoutId = setTimeout(() => { /* 操作 */ }, 3000);
  window.addEventListener('beforeunload', () => clearTimeout(timeoutId));
}

<!-- 优化前 -->
<img src="image.jpg" alt="产品图" />

<!-- 优化后 -->
<img 
  srcset="image.jpg 1x, image@2x.jpg 2x"
  sizes="(max-width: 768px) 300px, 800px"
  src="image.jpg"
  alt="高清产品图"
>

 前端项目优化配置
 Webpack生产模式配置
mode: 'production',
optimization: {
  runtimeChunk: 'single',
  splitChunks: {
    chunks: 'all',
    minSize: 30000,
    maxSize: 200000,
    minChunks: 1,
    maxAsyncRequests: 5,
    maxInitialRequests: 3,
    algorithm: 'matrix',
  }
}

// 优化前
document.addEventListener('click', handleEvent);
document.addEventListener('scroll', handleScroll);

// 优化后（防滥用）
const eventPrefix = 'data-seo-';
const listeners = {
  click: handleEvent,
  scroll: handleScroll
};

document.querySelectorAll(`*[${eventPrefix}event]`).forEach(el => {
  const type = el.dataset[eventPrefix + 'event'];
  if (type && listeners[type]) {
    el.addEventListener(type, listeners[type]);
  }
});