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HTML 

              
                <!DOCTYPE html>
<html>

<head>
  <title>8_常用注册页面的表单实例（含验证）.html</title>

  <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
  <meta http-equiv="description" content="this is my page">
  <meta http-equiv="content-type" content="text/html; charset=UTF-8">

  <!--<link rel="stylesheet" type="text/css" href="./styles.css">-->

  <style type="text/css">
    body {
      /*background-image: url(https://imgchr.com/content/images/system/home_cover_1552414407320_3a5f92.jpg);*/
      background-image: url('https://cdn.jsdelivr.net/gh/yansheng836/photos/universe.jpg');
      /*https://imgchr.com/content/images/system/home_cover_1587121321656_fce672.jpg
 https://imgtu.com/content/images/system/home_cover_1601010270144_8921bc.jpg
     https://cdn.jsdelivr.net/gh/yansheng836/photos/universe.jpg
 
      */
      background-repeat: no-repeat;
      /* 当内容高度大于图片高度时，背景图像的位置相对于viewport固定 */
      background-attachment: fixed;
      /*此条属性必须设置否则可能无效*/
      /* 让背景图基于容器大小伸缩 */
      background-size: cover;
      /* 设置背景颜色，背景图加载过程中会显示背景色 */
      background-color: #CCCCCC;
    }

    #user_reg {
      font-family: 微软雅黑;
      font-size: 40px;
      text-align: center;
      margin-top: 200px;
    }

    form {
      width: 500px;
      /*设置宽度，方便使其居中*/
      margin: 40px auto auto auto;
      /*上右下左*/
      font-size: 25px;
    }

    input {
      height: 30px;
      width: 12em;
      margin-top: 5px;
      margin-bottom: 5px;
    }

    /*input标签下的属性选择器*/

    input[type="submit"],
    input[type="reset"] {
      height: 25px;
      width: 5em;
      margin-top: 5px;
      margin-left: 6px;
    }
  </style>
</head>

<script type="text/javascript">
  //onblur失去焦点事件，用户离开输入框时执行 JavaScript 代码：
  //函数1：验证邮箱格式
  function validate_username(username) {
    //定义正则表达式的变量:邮箱正则
    var emailReg = /^\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*$/;
    //console.log(username);
    if (username != "" && username.search(emailReg) != -1) {
      document.getElementById("test_user").innerHTML = "<font color='green' size='3px'>√邮箱格式正确</font>";
    } else {
      document.getElementById("test_user").innerHTML = "<font color='red' size='3px'>邮箱格式错误</font>";
    }
  }
  //函数2：验证密码是否符合要求：匹配6位密码，由数字和字母组成：
  function validate_password(password) {
    //^(?![0-9]+$)(?![a-zA-Z]+$)[0-9A-Za-z]{6-10}$
    //测试密码：12345y
    var passwordReg = /^(?![0-9]+$)(?![a-zA-Z]+$)[0-9A-Za-z]{6}$/;
    if (password != "" && password.search(passwordReg) != -1) {
      document.getElementById("test_pw").innerHTML = "<font color='green' size='3px'>√密码格式正确</font>";
    } else {
      document.getElementById("test_pw").innerHTML = "<font color='red' size='3px'>密码格式错误</font>";
      alert("密码有6位，由数字和字母组成!");
    }
  }
  //函数3：验证两次输入的密码是否一样
  function validate_password2(password2) {
    var password = document.getElementById("password").value;
    //测试：console.log(password);
    //测试：console.log(password2);
    if (password == "") {
      document.getElementById("is_test_pw").innerHTML = "<font color='red' size='3px'>密码不为空</font>";
    } else if (password == password2) {
      document.getElementById("is_test_pw").innerHTML = "<font color='green' size='3px'>√两次输入的密码相同</font>";
    } else {
      document.getElementById("is_test_pw").innerHTML = "<font color='red' size='3px'>两次输入的密码不相同</font>";
      console.log("密码有6位，由数字和字母组成!");
    }
  }
  //函数4：验证表单是否已经填好
  function validate_form() {
    var username = document.getElementById("username").value;
    var password = document.getElementById("password").value;
    var password2 = document.getElementById("password2").value;
    //console.log("表单填写正确，可以正常提交！");
    //这三个，如果任何一个有问题，都返回false
    //[email protected]		12345y
    var emailReg = /^\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*$/;
    var passwordReg = /^(?![0-9]+$)(?![a-zA-Z]+$)[0-9A-Za-z]{6}$/;
    if (username != "" && emailReg.test(username)) {
      if (password != "" && passwordReg.test(password)) {
        if (password2 == password) {
          alert("信息填写正确，可以正常提交！");
          console.log("信息填写正确，可以正常提交！");
          return true;
        } else {
          alert("密码不一致，提交失败，请重新填写！");
          console.log("密码不一致，提交失败，请重新填写！");
          return false;
        }
      } else {
        alert("密码格式错误，提交失败，请重新填写！");
        console.log("密码格式错误，提交失败，请重新填写！");
        return false;
      }
    } else {
      alert("注册的账号不符合要求，提交失败，请重新填写！");
      console.log("注册的账号不符合要求，提交失败，请重新填写！");
      return false;
    }
  }
</script>

<body>
  <div id="user_reg">用户注册:</div>
  <form action="./servlet/RegisterServlet" method="post" name="form">
    <table>
      <tr>
        <td>请输入账号：</td>
        <td><input type="text" id="username" name="username" placeholder="只能用邮箱注册" onblur="validate_username(this.value)" /></td>
        <td id="test_user"></td>
      </tr>
      <tr>
        <td>请输入密码：</td>
        <td><input type="password" id="password" name="password" placeholder="6位密码由数字和字母组成" onblur="validate_password(this.value)" /></td>
        <td id="test_pw"></td>
      </tr>
      <tr>
        <td>请确认密码：</td>
        <td><input type="password" id="password2" name="password2" onblur="validate_password2(this.value)" /></td>
        <td id="is_test_pw"></td>
      </tr>
      <tr>
        <td></td>
        <td><input type="submit" id="submit_form" value="注册" onclick="return validate_form()" />
          <input type="reset" value="重置" />
        </td>
      </tr>
    </table>
  </form>
</body>

</html>
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