JSFiddle - React, Tailwind, and code Playground

HTML

<div id="myfirstdiv">
    <span>first contents</span>
    <span>first contents</span>
</div>
<div id="myseconddiv">
    <span>second contents</span>
    <span>second contents</span>
</div>

JavaScript

var contentofmyfirstdiv = $('#myfirstdiv').children().detach();
var contentofmyseconddiv = $('#myseconddiv').children().detach();

$('#myseconddiv').append(contentofmyfirstdiv);
$('#myfirstdiv').append(contentofmyseconddiv)