JSFiddle - React, Tailwind, and code Playground

HTML

<div class="foo" style="border:1px solid #444">
      <span class="field-with-fancyplaceholder">
      <label class="placeholder" for="pseudonym_session_unique_id" style="font-size: 13px;">
      <span>Email</span>
      </label>
      <input id="pseudonym_session_unique_id" class="text" type="text" size="30" name="pseudonym_session[unique_id]"></span>

      <br>
      <span class="field-with-fancyplaceholder">
      <label class="placeholder" for="pseudonym_session_password" style="font-size: 13px;">
      <span>Password</span>
      </label>
      <input id="pseudonym_session_password" class="text" type="password" size="30" name="pseudonym_session[password]">
      </span>

</div>

CSS

* {margin:5px !important; padding:5px !important}
.bar {border:3px dotted purple}

JavaScript

$('label:eq(0) span').text('user name');