Bootstrap有自定义的验证码样式，在前端页面可以直接使用，他的css、js在使用前要在开头引入
上代码：
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <!-- 告诉浏览器网页所识别的文件类型及语言类型 --> <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"> <title>登录</title> <!-- 让一些搜索引擎搜索到你的网页 --> <meta content=""> <meta content=""> <meta content="width=device-width, initial-scale=1"> <link href="https://cdn.bootcss.com/bootstrap/4.0.0-beta/css/bootstrap.min.css" > <script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.min.js"></script> <script src="https://cdn.bootcss.com/popper.js/1.12.5/umd/popper.min.js"></script> <script src="https://cdn.bootcss.com/bootstrap/4.0.0-beta/js/bootstrap.min.js"></script> <script src="https://www.jb51.net/tool.js"></script> <style> .carousel-inner img { width:100%; height:100%; } .jumbotron { margin-top: 10px; margin-bottom: 0px; padding-top: 10px; } #demo { width:100%; height: 500px; } .row { height: 264px; } .left { float: left; width: 70%; } .right { float: left; width: 30%; } .card { height: 340px; } .carousel-inner { height: 500px; } .footer { position: absolute; bottom: 0; height: 60px; } .jumheight1 { height: 100px; } .jumheight2 { height: 100px; } .end_name { margin-bottom: 5px; } .footer2 { padding-top: 210px; text-align: center; } .test{ margin-bottom: 75px; } .carousel-control-prev, .carousel-control-next{ bottom: 120px; } </style> </head> <body> <div> <form method="post" action="{:url('index/Login/doLogin')}"> <div> <h1>图书阅读网</h1> <p>一个免费的图书网站</p> </div> <!-- 轮播图 --> <!-- 指示符 --> <div> <div> <div data-ride="carousel"> <ul> <li data-target="#demo" data-slide-to="0"></li> <li data-target="#demo" data-slide-to="1"></li> <li data-target="#demo" data-slide-to="2"></li> </ul> <!-- 轮播图片 --> <div> <div> <img src="https://static.runoob.com/images/mix/img_fjords_wide.jpg"> </div> <div> <img src="https://static.runoob.com/images/mix/img_nature_wide.jpg"> </div> <div> <img src="https://static.runoob.com/images/mix/img_mountains_wide.jpg"> </div> </div> <!-- 左右切换按钮 --> <a href="#demo" data-slide="prev"> <span></span> </a> <a href="#demo" data-slide=next> <span></span> </a> </div> </div> <div> <!-- 登陆窗口 --> <div> <div> 用户登陆 </div> <div> <form> <table> <tr> <td> <label>电话号码：</label> </td> <td> <input type="text" pattern="^\d{11}" placeholder="请输入您的电话号码"> <!-- <input type="text" pattern="^\d{11}" placeholder="请输入您的电话号码" required> --> </td> </tr> <tr> <td> <label>密码:</label> </td> <td> <input type="password" placeholder="请输入您的密码"> </td> </tr> <tr> <td> <label for="captcha">验证码:</label> </td> <td> <input type="text" placeholder="请输入验证码"> <!-- 点击验证码更换 --> <br> <div><img src="https://www.jb51.net/{:captcha_src()}" alt="captcha"/></div> </td> </tr> </table> <div> <button type="submit" >登陆</button> <button type="submit" formaction="{:url('index/Repassword/index')}" >忘记密码？</button> </div> </form> </div> </div> </div> </div> </div> </div> <script> fieldTest(); </script> </body> </html>
效果图：
这里还有轮播图，点击验证码时会更新
可以使用在线HTML/CSS/JavaScript代码运行工具：测试上述代码运行效果。
PS：关于bootstrap布局，这里再为大家推荐一款本站的在线可视化布局工具供大家参考使用：