JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>
<script src="https://code.jquery.com/jquery-3.2.1.min.js"></script>
<div class="message message__current">
            <div class="message__date">27/04</div>
        <div class="message__body" data-for="main"
             data-tip="27/04 00:54" currentitem="false">test2
        </div>
</div>
<div class="message message__current message--grouped">
        <div class="message__body" data-for="main"
             data-tip="27/04 00:54" currentitem="false">test1
        </div>
</div>

JavaScript

$(function () {
  var result = [];

	$('.message.message__current .message__body').each(function (key, el) {
    result.push($(el).data().tip);
  });

  console.log(_.groupBy(result));
});