The answer
defer. jQuery is usually a dependency for other scripts. Use defer to guarantee it loads before scripts that depend on it. async would not guarantee order.
async and defer: Real-World Examples
Should jQuery be loaded with async or defer?
More FAQs in async and defer: Real-World Examples
<script src='react.js' defer></script><script src='react-dom.js' defer></script><script src='app.js' defer></script>. All deferred: download in parallel, execute in order (react first, app last).
<script src='analytics.js' async></script>. Analytics is independent (does not depend on other scripts or the DOM), so async is appropriate. It loads and runs whenever it is ready.
Yes. Use async for independent scripts (analytics, ads) and defer for dependent scripts (app logic). They do not interfere with each other. async scripts may run before or after deferred scripts.
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