How to use preload and preconnect techniques to improve the loading speed of critical resources?

When needing to prioritize loading critical resources that affect first-screen rendering,合理使用预加载（preload）和预连接（preconnect）技术可有效提升资源加载速度。preload is used to specify the提前加载当前页面必需的关键资源, while preconnect is used to提前建立与跨域资源服务器的连接, reducing handshake delays for subsequent requests. Key resource types: - First-screen CSS/JS: Style sheets or scripts crucial for rendering, use `<link rel="preload" href="critical.css" as="style">` to提前加载, avoiding rendering blocking. - Font files: Specify `as="font"` and set `crossorigin` via preload to解决字体加载延迟导致的文本闪烁（FOIT）. - Cross-origin resources: For cross-origin resources such as CDNs and third-party APIs, use `<link rel="preconnect" href="https://cdn.example.com">` to提前建立TCP连接和SSL握手, shortening the time taken for subsequent requests. It is recommended to identify critical resources using page performance analysis tools (such as Lighthouse) to avoid resource waste caused by excessive preloading. Prioritize using preload for resources with long loading chains or large sizes, and use preconnect for high-frequency cross-origin domain names to balance loading efficiency and resource consumption.