Bootstrap自定义表单验证提交时如何定位未填写字段？

我懂你遇到的痛点——原生表单提交时会自动跳转到第一个未填写的必填字段，但Bootstrap的自定义验证脚本默认只添加了样式提示，没带上这个自动聚焦的功能。别担心，咱们只需要给验证脚本加几行代码就能搞定！

问题根源 #

Bootstrap的自定义验证脚本里，当表单验证不通过时调用了event.preventDefault()和event.stopPropagation()，这阻止了浏览器原生的表单提交行为，包括自动聚焦到无效字段的功能。所以我们需要手动实现这个聚焦逻辑。

解决方案 #

修改你的验证脚本，在标记表单为was-validated之前，找到第一个无效的表单元素并让它获得焦点。这里我们可以用:invalid选择器来定位无效元素，然后调用focus()方法。

修改后的完整代码 #

JavaScript部分

// Example starter JavaScript for disabling form submissions if there are invalid fields
(function() {
  'use strict';
  window.addEventListener('load', function() {
    // Fetch all the forms we want to apply custom Bootstrap validation styles to
    var forms = document.getElementsByClassName('needs-validation');
    // Loop over them and prevent submission
    var validation = Array.prototype.filter.call(forms, function(form) {
      form.addEventListener('submit', function(event) {
        if (form.checkValidity() === false) {
          event.preventDefault();
          event.stopPropagation();
          // 新增：找到第一个无效元素并聚焦
          const firstInvalidElement = form.querySelector(':invalid');
          if (firstInvalidElement) {
            firstInvalidElement.focus();
            // 可选：平滑滚动到元素位置，提升用户体验
            firstInvalidElement.scrollIntoView({ behavior: 'smooth', block: 'center' });
          }
        }
        form.classList.add('was-validated');
      }, false);
    });
  }, false);
})();

HTML部分（补全你提供的截断代码）

<html>
<head>
  <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.0/css/bootstrap.min.css" integrity="sha384-9gVQ4dYFwwWSjIDZnLEWnxCjeSWFphJiwGPXr1jddIhOegiu1FwO5qRGvFXOdJZ4" crossorigin="anonymous">
</head>
<body>
  <form class="needs-validation" novalidate>
    <div class="form-row">
      <div class="col-md-4 mb-3">
        <label for="validationCustom01">First name</label>
        <input type="text" class="form-control" id="validationCustom01" placeholder="First name" value="Mark" required>
        <div class="valid-feedback">Looks good!</div>
      </div>
      <div class="col-md-4 mb-3">
        <label for="validationCustom02">Last name</label>
        <input type="text" class="form-control" id="validationCustom02" placeholder="Last name" value="Otto" required>
        <div class="valid-feedback">Looks good!</div>
      </div>
      <div class="col-md-4 mb-3">
        <label for="validationCustomUsername">Username</label>
        <div class="input-group">
          <div class="input-group-prepend">
            <span class="input-group-text" id="inputGroupPrepend">@</span>
          </div>
          <input type="text" class="form-control" id="validationCustomUsername" placeholder="Username" aria-describedby="inputGroupPrepend" required>
          <div class="invalid-feedback">Please choose a username.</div>
        </div>
      </div>
    </div>
    <div class="form-row">
      <div class="col-md-6 mb-3">
        <label for="validationCustom03">City</label>
        <input type="text" class="form-control" id="validationCustom03" placeholder="City" required>
        <div class="invalid-feedback">Please provide a valid city.</div>
      </div>
      <div class="col-md-3 mb-3">
        <label for="validationCustom04">State</label>
        <input type="text" class="form-control" id="validationCustom04" placeholder="State" required>
        <div class="invalid-feedback">Please provide a valid state.</div>
      </div>
      <div class="col-md-3 mb-3">
        <label for="validationCustom05">Zip</label>
        <input type="text" class="form-control" id="validationCustom05" placeholder="Zip" required>
        <div class="invalid-feedback">Please provide a valid zip.</div>
      </div>
    </div>
    <div class="form-group">
      <div class="form-check">
        <input class="form-check-input" type="checkbox" value="" id="invalidCheck2" required>
        <label class="form-check-label" for="invalidCheck2">Agree to terms and conditions</label>
        <div class="invalid-feedback">You must agree before submitting.</div>
      </div>
    </div>
    <button class="btn btn-primary" type="submit">Submit form</button>
  </form>
</body>
</html>

效果说明 #

现在当你提交表单时：

1. 表单会阻止默认提交行为，保留Bootstrap的自定义验证样式（红色边框、错误提示）
2. 页面会自动跳转到第一个未填写/不符合要求的字段，并让它获得焦点，和原生表单的行为完全一致

内容的提问来源于stack exchange，提问作者Keerthi Reddy Yeruva