What front-end optimization measures are effective in reducing First Input Delay (FID)?

When needing to reduce First Input Delay (FID), effective front-end optimization measures typically focus on reducing main thread blocking and optimizing interaction response efficiency, with core aspects including reducing non-critical JavaScript execution time, optimizing event handling logic, and prioritizing the loading of critical resources. Main Thread减负: Avoid executing uncompressed or unsplit large JavaScript files during initial screen loading. Code Splitting can be used to load only the scripts necessary for the current page, reducing initial parsing and compilation time. Delay Non-Critical Resources: Use async/defer attributes to asynchronously load non-initial screen JavaScript, or delay loading low-priority components through dynamic import(), to avoid blocking HTML parsing and the main thread. Optimize Event Handlers: Apply Debounce or Throttle to high-frequency trigger events (such as resize, scroll) to reduce unnecessary function executions and lower main thread load. Web Workers Offloading: Move tasks such as data processing and complex calculations to Web Workers, allowing the main thread to focus on user interaction responses and avoiding delays caused by compute-intensive operations. During implementation, it is recommended to monitor main thread activities with performance tools like Lighthouse, prioritize optimizing critical path resources that affect users' first interaction, and gradually improve page response speed.