JSFiddle - React, Tailwind, and code Playground

HTML

<span id="ex1" >
<img width="794px" height="593px" src="images/crateria.png" style="margin:0;" onmouseover="javascript:mostra();" alt="Crateria" />
</span>

JavaScript

function mostra(){
    var span = document.getElementById("ex1");
    var contemMapa = span.lastChild.nodeName === 'MAP';
    if(!contemMapa) {
        var para = document.createElement("map");
        para.setAttribute("name", "crateria-map");
        document.getElementById("ex1").appendChild(para);
    }
}