<!DOCTYPE html> <html lang="en"> <head><meta charset="UTF-8"><title>jq之demo</title><!--线上jq库--><script src="https://code.jquery.com/jquery-3.4.1.min.js"></script><script>$(document).ready(function(){/*获得焦点*/$("#test").hover(function(){/*弹出1*/alert(1);},function () {alert("你离开了")});});</script> </head> <body> <h2>这是标题</h2> <p>喔喔</p> <p>我</p> <p id="test">我2</p> </body> </html>