JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container" id = "theParent">
    <div id="div1" class="content">aaa<br>aaa</div>
    <div id="div2" class="content">bbb<br><br>bbb</div>
    <div id="div3" class="content">ccc</div>
 
    <div id="div4" class="content">ddd</div>
</div>

CSS

.container {
    position: absolute;
    top: 10px;
    left: 10px;
    right: 10px;
    bottom: 10px;
    border: 1px solid red;
}

.content {
    position: relative;
    top: 0px;
    left: 5px;
    width: 200px;
    height: auto;
    border: 1px solid blue;
    margin: 3px;
}

JavaScript

theParent = document.getElementById("theParent");
theKid = document.createElement("div");
theKid.setAttribute("id","div5");
theKid.setAttribute("class","content");
theKid.innerHTML = 'eee';

// append theKid to the end of theParent
theParent.appendChild(theKid);

// prepend theKid to the beginning of theParent
theParent.insertBefore(theKid, theParent.firstChild);