How to properly add mouseover functionality in javascript. You can add onmouseover keyword argument in the element.

<div onmouseover="processMouseOver(this)">
    Your Children Element Here.
</div>

Make sure to call this then only function accepts element as argument otherwise will be null.

This is how the javascript code look like.

function processMouseOver(element) {
    console.log(element)
}

addEventListener works only if the element is already available in the DOM. If you add new element append to the DOM then chances are the addEventListener will not work.