javascript - 在输入焦点上更改标签的字体大小

Question

我正在尝试在输入焦点上实现 float 标签，就像这个带有样式组件的标签一样: https://jsfiddle.net/273ntk5s/3650/

但是我的表单是动态加载的，所以先加载标签，然后再加载输入输出。之后加载输入类型文本时，输入焦点更改不起作用。有没有办法做到这一点？我也用过 jQuery，仍然没有运气。CSS:

var oldSize;
$('#FirstName').focus(function() {
  oldSize = $("label[for='FirstName']").css('font-size');
  $("label[for='FirstName']").css('font-size', 12);
});
$('#FirstName').blur(function() {
  $("label[for='FirstName']").css('font-size', oldSize);
});

.inputText {
  font-size: 14px;
  width: 200px;
  height: 35px;
}

.floating-label {
  position: absolute;
  pointer-events: none;
  font-size: 14px;
  transition: 0.2s ease all;
}
input[id='FirstName']:focus + .floating-label
{
    font-size: 11px;
}

<div>
  <label for="FirstName" class="mktoLabel mktoHasWidth floating-label" style="width: 100px;">First name:</label>
  <input id="FirstName" name="FirstName" maxlength="255" type="text" class="mktoField mktoTextField mktoHasWidth mktoRequired mktoInvalid inputText" style="width: 150px;">

</div>

Answer 1

font-size 接受格式为 ##px 的值。单靠数字是行不通的。您还需要在您的 fiddle 中正确包含 jQuery。

var oldSize;
$('#FirstName').focus(function() {
  oldSize = $("label[for='FirstName']").css('font-size');
  $("label[for='FirstName']").css('font-size', '42px');
});
$('#FirstName').blur(function() {
  $("label[for='FirstName']").css('font-size', oldSize);
});

.inputText {
  font-size: 14px;
  width: 200px;
  height: 35px;
}

.floating-label {
  position: absolute;
  pointer-events: none;
  font-size: 14px;
  transition: 0.2s ease all;
}
input[id='FirstName']:focus + .floating-label
{
    font-size: 11px;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div>
  <label for="FirstName" class="mktoLabel mktoHasWidth floating-label" style="width: 100px;">First name:</label>
  <input id="FirstName" name="FirstName" maxlength="255" type="text" class="mktoField mktoTextField mktoHasWidth mktoRequired mktoInvalid inputText" style="width: 150px;">

</div>