隐藏输入的标签，不带属性“required”（浮动标签）

I have this code:

我有这个代码：

<span class="field">
<input type="text" id="first-name" placeholder="First Name" required />
<label for="first-name">First Name</label>
</span>

<span class="field">
<input type="text" id="last-name" placeholder="Last Name" />
<label for="last-name">Last Name</label>
</span>
<span class="fiel