[jQuery] how to use onfocus event with jQuery ?

[jQuery] how to use onfocus event with jQuery ?

<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">hi all, <div>
</div><div>    i'm new to jQuery,    how to use onfocus event with jQuery ? </div><div>
</div><div>    Could you give me a demo ?</div><div>
</div><div>    Thank you!</div><div>
</div><div>Alex</div></body></html>