JavaScript Defer and Async vs Lazy Loading

Developers should use defer and async to improve page load times and user experience, especially for scripts that are not critical for initial rendering meets developers should use lazy loading when building applications with large datasets, media-heavy content, or complex user interfaces to enhance performance and user experience. Here's our take.

JavaScript Defer and Async

Nice Pick

Developers should use defer and async to improve page load times and user experience, especially for scripts that are not critical for initial rendering

Pros

• Use 'defer' for scripts that depend on the DOM being fully loaded, such as interactive features, and 'async' for independent scripts like analytics or ads that don't rely on other elements
• Related to: javascript, html

Cons

• Specific tradeoffs depend on your use case

Lazy Loading

Developers should use lazy loading when building applications with large datasets, media-heavy content, or complex user interfaces to enhance performance and user experience

Pros

• It is particularly useful in web development for loading images, videos, or JavaScript modules only when they become visible in the viewport, reducing bandwidth and speeding up page loads
• Related to: code-splitting, dynamic-imports

Cons

• Specific tradeoffs depend on your use case

The Verdict

Use JavaScript Defer and Async if: You want use 'defer' for scripts that depend on the dom being fully loaded, such as interactive features, and 'async' for independent scripts like analytics or ads that don't rely on other elements and can live with specific tradeoffs depend on your use case.

Use Lazy Loading if: You prioritize it is particularly useful in web development for loading images, videos, or javascript modules only when they become visible in the viewport, reducing bandwidth and speeding up page loads over what JavaScript Defer and Async offers.

The Bottom Line

JavaScript Defer and Async wins

Developers should use defer and async to improve page load times and user experience, especially for scripts that are not critical for initial rendering