<!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>$(document).ready(function(){$("input").focus(function () {$(this).css("background-color","blue");})/*失去焦点*/$("input").blur(function () {$(this).css("background-color","yellow");})});</script>
</head>
<body>
name:<input type="text" name="fullname"><br>
email:<input type="text" name="email">
</body>
</html>