JSFiddle - React, Tailwind, and code Playground

HTML

<div id="mydiv1">
    <div id="div1">1</div>
    <div id="div2">2</div>
</div>
<div id="mydiv2"></div>

JavaScript

function copyDiv() {
    var firstDivContent = document.getElementById('mydiv1');
    var secondDivContent = document.getElementById('mydiv2');
    secondDivContent.innerHTML = firstDivContent.innerHTML;
}

//Call copyDiv on body="onload"
copyDiv();