javascript - 带有标签的自定义 Material 样式输入不起作用

Question

我创建了一个带有标签的 Material 设计风格的输入表单，这里是一个JSfiddle demo它似乎工作正常，但只有当我在输入标签中添加 required 时它才有效，如果我从输入中删除 required 它停止工作，不知道为什么，有人可以吗进去看看？

提前致谢。

.ttl{
  font-size:16px;
  margin:10px 0;
}
.form-row:nth-child(1){
  margin-top:50px;
}
.form-row {
  margin-top: 20px;
  margin-bottom: 20px;
  float: left;
  width: 100%;
  position: relative;
}
.form-group input {
  height: 2.5rem;
}
.form-group .control-label {
  position: absolute;
  top: 0.25rem;
  pointer-events: none;
  padding-left: 0.125rem;
  z-index: 1;
  color: #696969;
  font-size: 1.750rem;
  font-weight: normal;
  -webkit-transition: all 0.28s ease;
  transition: all 0.28s ease;
  font-family: 'Montserrat-Regular';
  text-align: center;
  width: 100%;
}
.form-group .bar {
  position: relative;
  border-bottom: 0.0625rem solid #999;
  display: block;
}
.form-group .bar::before {
  content: '';
  height: 0.125rem;
  width: 0;
  left: 50%;
  bottom: -0.0625rem;
  position: absolute;
  background: #40b8f1;
  -webkit-transition: left 0.28s ease, width 0.28s ease;
  transition: left 0.28s ease, width 0.28s ease;
  z-index: 2;
}
.form-group input, .form-group textarea {
  display: block;
  background: none;
  padding: 0.125rem 0.125rem 0.0625rem;
  font-size: 1.750rem;
  border-width: 0;
  border-color: transparent;
  line-height: 2;
  width: 100%;
  color: transparent;
  -webkit-transition: all 0.28s ease;
  transition: all 0.28s ease;
  box-shadow: none;
  text-align: center;
}
.form-group select ~ .control-label, .form-group input:focus ~ .control-label, .form-group input:valid ~ .control-label, .form-group input.form-file ~ .control-label, .form-group input.has-value ~ .control-label, .form-group textarea:focus ~ .control-label, .form-group textarea:valid ~ .control-label, .form-group textarea.form-file ~ .control-label, .form-group textarea.has-value ~ .control-label {
  font-size: 1.750rem;
  color: gray;
  top: -2.750rem;
  left: 0;
}
.form-group select:focus ~ .bar::before, .form-group input:focus ~ .bar::before, .form-group textarea:focus ~ .bar::before {
  width: 100%;
  left: 0;
}

<p class="ttl">Without required it doesn't work</p>
<div class="form-row">
  <div class="form-group">
    <input type="text" name="student">
    <label for="input" class="control-label">Label Title here</label>
    <i class="bar"></i>
  </div>
</div>
<p class="ttl">With required it works</p>
<div class="form-row">
  <div class="form-group">
    <input required type="text" name="student">
    <label for="input" class="control-label">Label Title here</label>
    <i class="bar"></i> 
  </div>
</div>

Answer 1

从输入焦点的样式中删除 .form-group input:valid ~ .control-label

对此的更改

 .form-group select ~ .control-label, .form-group input:focus ~   .control-label, .form-group input.form-file ~ .control-label, .form-group input.has-value ~ .control-label, .form-group textarea:focus ~ .control-label, .form-group textarea:valid ~ .control-label, .form-group textarea.form-file ~ .control-label, .form-group textarea.has-value ~       .control-label {
 font-size: 1.750rem;
 color: gray;
 top: -2.750rem;
 left: 0;
}

https://jsfiddle.net/fy577w6b/3/

或者在输入无效时为控件标签添加样式。