What are the differences between async and defer attributes in script tags?

Can you explain the difference between async and defer attributes in script tags?

Sure! The async attribute allows the script to be downloaded in parallel with the page parsing, and it will execute as soon as it's downloaded. The defer attribute also downloads the script in parallel, but it waits to execute until the HTML document is fully parsed.

When should I use async over defer?

You should use async when the script is independent and doesn't rely on other scripts or the DOM being fully loaded. Use defer when the script depends on the DOM being fully parsed or when it relies on other scripts.

Are there any performance implications of using one over the other?

Yes, using async can improve performance for independent scripts since they load and execute immediately. However, if scripts depend on each other, using defer ensures they run in the correct order after the document is ready.

Can I use both attributes on the same script tag?

No, you cannot use both async and defer on the same script tag. If both are present, only async will be applied.