JSFiddle - React, Tailwind, and code Playground

HTML

<img id="demo_image" src="smiley.gif" alt="Smiley face" width="42" height="42" onmouseover="changeImage(this)" onmouseout="changeImage(this)" data-image2="http://mw2.google.com/mw-panoramio/photos/small/17287086.jpg">

JavaScript

function changeImage(img) {
    img = $(img);
   var in_url = img.attr('src');
   var out_url =  img.attr('data-image2');
    console.log(out_url)
   //img.attr('src', in_url).attr('data-image2', out_url);
}