实例

使用 .needs-validation，它将在表单提交之后验证缺少的内容。这里需要添加一些 JavaScript 代码才能使代码正常工作：

<form action="" class="needs-validation" novalidate>
  <div class="form-group">
    <label for="uname">Username:</label>
    <input type="text" class="form-control" id="uname" placeholder="Enter username" name="uname" required>
    <div class="valid-feedback">验证成功！</div>
    <div class="invalid-feedback">请输入用户名！</div>
  </div>
  <div class="form-group">
    <label for="pwd">Password:</label>
    <input type="password" class="form-control" id="pwd" placeholder="Enter password" name="pswd" required>
    <div class="valid-feedback">验证成功！</div>
    <div class="invalid-feedback">请输入密码！</div>
  </div>
  <div class="form-group form-check">
    <label class="form-check-label">
      <input class="form-check-input" type="checkbox" name="remember" required> 同意协议
      <div class="valid-feedback">验证成功！</div>
      <div class="invalid-feedback">同意协议才能提交。</div>
    </label>
  </div>
  <button type="submit" class="btn btn-primary">提交</button>
</form>
 
<script>
// 如果验证不通过禁止提交表单
(function() {
  'use strict';
  window.addEventListener('load', function() {
    // 获取表单验证样式
    var forms = document.getElementsByClassName('needs-validation');
    // 循环并禁止提交
    var validation = Array.prototype.filter.call(forms, function(form) {
      form.addEventListener('submit', function(event) {
        if (form.checkValidity() === false) {
          event.preventDefault();
          event.stopPropagation();
        }
        form.classList.add('was-validated');
      }, false);
    });
  }, false);
})();
</script>