JSFiddle - React, Tailwind, and code Playground

HTML

<div src="test1"></div>
<div src="test2"></div>
<div src="test3"></div>

JavaScript

window.onload = function() {
    var att, i, elie = document.getElementsByTagName("div");

    for (i = 0; i < elie.length; ++i)
    {
        att = elie[i].getAttribute("src");
        elie[i].setAttribute("data", att);
        elie[i].removeAttribute("src");        
    }
    
    alert(document.getElementsByTagName("body")[0].innerHTML);
}