css - 如何在 bootstrap 4 css 中实现验证？

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我在 bootstrap 4 文档中看到了这个例子:

https://v4-alpha.getbootstrap.com/components/forms/#validation

<div class="form-group has-success">
  <label class="form-control-label" for="inputSuccess1">Input with success</label>
  <input type="text" class="form-control form-control-success" id="inputSuccess1">
  <div class="form-control-feedback">Success! You've done it.</div>
  <small class="form-text text-muted">Example help text that remains unchanged.</small>
 </div>
 <div class="form-group has-warning">
  <label class="form-control-label" for="inputWarning1">Input with warning</label>
  <input type="text" class="form-control form-control-warning" id="inputWarning1">
   <div class="form-control-feedback">Shucks, check the formatting of that and try again.</div>
  <small class="form-text text-muted">Example help text that remains unchanged.</small>
</div>
<div class="form-group has-danger">
  <label class="form-control-label" for="inputDanger1">Input with danger</label>
  <input type="text" class="form-control form-control-danger" id="inputDanger1">
  <div class="form-control-feedback">Sorry, that username's taken. Try another?</div>
  <small class="form-text text-muted">Example help text that remains unchanged.</small>
</div>

但是，编辑没有颜色

文档说我必须加载 CSS，但在 CSS 中缺少 has-danger 类

https://stackpath.bootstrapcdn.com/bootstrap/4.1.0/css/bootstrap.min.css

代替在 bootstrap 3 的 CSS 中，类存在

https://getbootstrap.com/docs/3.3/dist/css/bootstrap.min.css

事实上，如果我使用 bootstrap 3 的 css，编辑内容是彩色的

如何在 bootstrap 4 中使用 has-danger 类？我需要使用 css 而不是 Sass

最佳答案

类 has-danger 不再用于 bootstrap4(已弃用) 在输入中使用 is-invalid 选择器并在代码中包含 class="invalid-feedback"