JAVASCRIPT

javascript appendchild before

Node.insertBefore()
// js
const parent = document.querySelector("#parentElement");
const insertBeforeThisElem = document.querySelector("#childElement");
const newElement = document.createElement("span")

parent.insertBefore(newElement, insertBeforeThisElem);

// file.html
<div id="parentElement">
	// this exists only after running code above
    // <span></span>
   <span id="childElement">foo bar</span>
</div>