The power of JavaScript makes it a key element of interactive experiences on the web. However, efficient code writing is not only about function implementation, but also about speed. In 2025, users will demand higher application speeds, and even slight delays may lead to user churn.

The following ten JavaScript performance optimization tips will help you create fast and smooth applications:

1. Take advantage of ES2025 new features

ES2025 introduces features such as array grouping, improved JSON modules, and symbols as WeakMap keys to simplify code and improve performance. Also, be sure to review your build process to avoid outdated polyfills impacting your production code.

2. Measure first, then optimize

Don’t optimize blindly. Leverage tools like Lighthouse, WebPageTest, and Chrome DevTools to identify performance bottlenecks and focus on key metrics like LCP, FID, and CLS. Data-driven optimization can achieve twice the result with half the effort.

3. Reduce rendering-blocking scripts

JavaScript that blocks the main thread will slow down page loading. To do this, load your script using the async or defer attribute, load critical code first, lazily load the rest, and minify JavaScript files. Tools like Esbuild or Vite can simplify this process.

4. Optimize DOM operations

Frequent DOM operations can seriously affect performance. Update elements in batches to avoid repeatedly querying the DOM in a loop. Frameworks like Svelte or SolidJS minimize direct DOM interaction by compiling components into optimized JavaScript code.

5. Reasonably split the code

Large JavaScript bundles are deprecated. Users don't need to load the entire app at once, just the part they are currently interacting with. Use code splitting techniques to load smaller chunks of JavaScript code by route or component, and tree shaking to remove unused code. The advantage of HTTP/3 is that multiple small blocks of code load faster than a single large block of code.

6. Proper use of asynchronous operations

async/await simplifies the code, but overuse may cause event loop tasks to pile up. For parallel tasks, use Promise.all, which is faster and avoids redundant overhead.

7. Make full use of cache

Caching is the key to improving the speed of repeated access: use Service Workers to cache static resources and store non-sensitive data in IndexedDB or localStorage. For APIs, implement the stale-while-revalidate strategy to ensure users get the latest data while avoiding long waits.

8. Carefully design status management

Modern libraries like Zustand and Jotai simplify state management. But avoid over-engineering and only store necessary global state. Redundant or deeply nested state can cause unnecessary re-rendering, especially in large applications.

9. Reduce loop overhead

For large data sets, avoid using .forEach and consider using for...of or .map() for conversion, which are more readable and often faster. Precompute values ??outside the loop whenever possible.

10. Extended test environment

Your high-end device is not typical for the average user. Use tools like BrowserStack or Lighthouse to test your app on low-performance devices and network conditions. Performance testing in real environments is essential.

Follow the above tips, measure regularly, and stay tuned for new tools and technologies to stay ahead of the curve in this era of rapid JavaScript development.

Do you have any other optimization tips? Feel free to share in the comment area.

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