HTML/JavaScript表单验证与条件弹窗显示教程

<!-- 模态弹窗区域 -->
<div id="myModal" class="modal">
  <div class="modal-content">
    <div class="modal-header">
      <h2>Application Accepted</h2>
      <span class="close">&times;</span>
    </div>
    <div class="modal-body">
      <p>Go Back To Home Page <a href="home">Home</a></p>
    </div>
  </div>
</div>

<!-- 表单区域 -->
<form method="post" name="f1" action="">
  <h2 style="padding-left:50px">Application Form</h2>
  <table>
    <tr>
      <td><label for="uname">Name</label></td>
      <td><input type="text" id="uname" name="username" required></td>
    </tr>
    <tr>
      <td><label for="date">Date Of Birth</label></td>
      <td><input type="date" id="date" name="date" required></td>
    </tr>
    <tr>
      <td><label>Gender</label></td>
      <td>
        <label><input type="radio" value="female" name="gender" required> Female</label>
        <label><input value="male" type="radio" name="gender"> Male</label>
      </td>
    </tr>
    <tr>
      <td><label for="district">District</label></td>
      <td>
        <select name="district" id="district">
          <option value="">---Select District---</option>
        </select>
      </td>
    </tr>
    <tr>
      <td><label for="city">City</label></td>
      <td>
        <select name="city" id="city">
          <option value="">---Select District First---</option>
        </select>
      </td>
    </tr>
    <tr>
      <td></td>
      <td>
        <button type="submit" id="myBtn" class="cancelbtn" onclick="return valid();">SUBMIT</button>
      </td>
    </tr>
  </table>
</form>

body {
  font-family: Arial, Helvetica, sans-serif;
}

form {
  border: 3px solid #f1f1f1;
  padding-left: 290px; /* 示例布局调整 */
}

input[type=text],
input[type=date],
select {
  width: 75%;
  padding: 5px 10px;
  margin: 8px 0;
  display: inline-block;
  border: 1px solid #ccc;
  box-sizing: border-box;
  height: 30px; /* 针对select */
  text-align: center; /* 针对select */
}

button {
  background-color: #FF5733;
  color: white;
  padding: 10px 15px;
  margin: 8px 0;
  border: none;
  cursor: pointer;
  width: 100px;
  border-radius: 15px;
}

button:hover {
  opacity: 0.8;
}

/* 模态弹窗样式 */
.modal {
  display: none; /* 默认隐藏 */
  position: fixed;
  z-index: 1;
  padding-top: 100px;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  overflow: auto;
  background-color: rgb(0, 0, 0);
  background-color: rgba(0, 0, 0, 0.4); /* 半透明背景 */
}

.modal-content {
  position: relative;
  background-color: #fefefe;
  margin: auto;
  padding: 0;
  border: 1px solid #888;
  width: 50%;
  box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2), 0 6px 20px 0 rgba(0, 0, 0, 0.19);
  -webkit-animation-name: animatetop;
  -webkit-animation-duration: 0.4s;
  animation-name: animatetop;
  animation-duration: 0.4s;
}

/* 动画效果 */
@-webkit-keyframes animatetop {
  from { top: -300px; opacity: 0; }
  to { top: 0; opacity: 1; }
}

@keyframes animatetop {
  from { top: -300px; opacity: 0; }
  to { top: 0; opacity: 1; }
}

.close {
  color: white;
  float: right;
  font-size: 28px;
  font-weight: bold;
}

.close:hover,
.close:focus {
  color: #000;
  text-decoration: none;
  cursor: pointer;
}

.modal-header {
  padding: 10px 15px;
  background-color: #5cb85c;
  color: white;
}

.modal-body {
  padding: 10px 15px;
  text-align: center;
}

var subObject = {
  "place1": ["place1", "place2", "place3"],
  "place2": ["place4", "place4"],
};

window.onload = function() {
  var distSel = document.getElementById("district");
  var citySel = document.getElementById("city");

  // 填充区县下拉菜单
  for (var x in subObject) {
    distSel.options[distSel.options.length] = new Option(x, x);
  }

  // 区县选择变化时，动态填充城市下拉菜单
  distSel.onchange = function() {
    citySel.length = 1; // 重置城市下拉菜单，只保留默认选项
    var z = subObject[distSel.value];
    if (z) { // 确保有对应城市数据
      for (var i = 0; i < z.length; i++) {
        citySel.options[citySel.options.length] = new Option(z[i], z[i]);
      }
    }
  };

  // 模态弹窗的事件监听器应在此处初始化，而不是在valid()函数内部
  var modal = document.getElementById("myModal");
  var span = document.getElementsByClassName("close")[0];

  // 点击关闭按钮时隐藏模态弹窗
  span.onclick = function() {
    modal.style.display = "none";
  };

  // 点击模态弹窗外部区域时隐藏模态弹窗
  window.onclick = function(event) {
    if (event.target == modal) {
      modal.style.display = "none";
    }
  };
};

// 注意：modal, span 等变量需要在全局或window.onload中定义，以便valid()函数访问
// 修正后的JavaScript代码如下：

var subObject = {
  "place1": ["place1", "place2", "place3"],
  "place2": ["place4", "place4"],
};

var modal; // 全局声明modal变量
var span;  // 全局声明span变量

window.onload = function() {
  var distSel = document.getElementById("district");
  var citySel = document.getElementById("city");

  for (var x in subObject) {
    distSel.options[distSel.options.length] = new Option(x, x);
  }
  distSel.onchange = function() {
    citySel.length = 1;
    var z = subObject[distSel.value];
    if (z) {
      for (var i = 0; i < z.length; i++) {
        citySel.options[citySel.options.length] = new Option(z[i], z[i]);
      }
    }
  };

  // 在页面加载时初始化模态弹窗相关的DOM元素和事件监听器
  modal = document.getElementById("myModal");
  span = document.getElementsByClassName("close")[0];

  span.onclick = function() {
    modal.style.display = "none";
  };

  window.onclick = function(event) {
    if (event.target == modal) {
      modal.style.display = "none";
    }
  };
};

function valid() {
  // 访问表单元素时使用其name属性，如f1.username
  if (f1.username.value === "") {
    alert('请输入姓名');
    f1.username.focus();
    return false;
  } else if (f1.date.value === "") {
    alert('请输入出生日期');
    f1.date.focus();
    return false;
  } else if (f1.gender.value === "") {
    alert('请选择性别');
    f1.gender.focus();
    return false;
  } else if (f1.district.value === "") {
    alert('请选择区县');
    f1.district.focus();
    return false;
  } else if (f1.city.value === "") {
    alert('请选择城市');
    f1.city.focus();
    return false;
  } else {
    // 所有验证通过，显示模态弹窗
    if (modal) { // 确保modal元素已加载
      modal.style.display = "block";
    }
    // 阻止表单的默认提交行为
    return false;
  }
}

<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>表单验证与弹窗示例</title>
    <link rel="stylesheet" href="style.css">
</head>
<body>

    <!-- 模态弹窗区域 -->
    <div id="myModal" class="modal">
      <div class="modal-content">
        <div class="modal-header">
          <h2>Application Accepted</h2>
          <span class="close">&times;</span>
        </div>
        <div class="modal-body">
          <p>Go Back To Home Page <a href="home">Home</a></p>
        </div>
      </div>
    </div>

    <!-- 表单区域 -->
    <form method="post" name="f1" action="">
      <h2 style="padding-left:50px">Application Form</h2>
      <table>
        <tr>
          <td><label for="uname">Name</label></td>
          <td><input type="text" id="uname" name="username" required></td>
        </tr>
        <tr>
          <td><label for="date">Date Of Birth</label></td>
          <td><input type="date" id="date" name="date" required></td>
        </tr>
        <tr>
          <td><label>Gender</label></td>
          <td>
            <label><input type="radio" value="female" name="gender" required> Female</label>
            <label><input value="male" type="radio" name="gender"> Male</label>
          </td>
        </tr>
        <tr>
          <td><label for="district">District</label></td>
          <td>
            <select name="district" id="district">
              <option value="">---Select District---</option>
            </select>
          </td>
        </tr>
        <tr>
          <td><label for="city">City</label></td>
          <td>
            <select name="city" id="city">
              <option value="">---Select District First---</option>
            </select>
          </td>
        </tr>
        <tr>
          <td></td>
          <td>
            <button type="submit" id="myBtn" class="cancelbtn" onclick="return valid();">SUBMIT</button>
          </td>
        </tr>
      </table>
    </form>

    <script src="script.js"></script>
</body>
</html>