W3School TIY Editor
W3School 在线教程
改变方向
暗黑模式
运行代码
<!DOCTYPE html> <html> <head> <style> input:optional { background-color: lightgreen; } input:required { background-color: pink; border-color: red; } .req { color: red; } </style> </head> <body> <h1>:optional 和 :required 演示</h1> <form> <label for="name">姓名：</label><br> <input id="name" name="name" type="text" /><br> <label for="email">邮箱：<span class="req">*</span></label><br> <input id="email" name="email" type="email" required /><br> <label for="country">国家：</label><br> <input id="country" name="country" type="text" /> <p><span class="req">*</span> 必填字段</p> </form> </body> </html>