JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/jquery-2.2.4.js"></script>
<div id="block">
    <div class="block">
        <div class="block_wrapper">
            <div class="block_item">aaa</div>
            <div class="block_item">aaa</div>
        </div>
    </div>
</div>

<button onclick="removewrapper()">
click
</button>

JavaScript

removewrapper = function(){
	var blockwrapper = $('#block .block_wrapper');
  if (blockwrapper.length){
  	var content = $(blockwrapper).html();
    var parent = $(blockwrapper).parent();
    $(blockwrapper).remove();
    $(parent).html(content);
  }
}