JSFiddle - React, Tailwind, and code Playground
HTML
<div id="texty" onmouseover="if (document.getElementById('texty').innerHTML!='mail@fuze.pro') {document.getElementById('texty').innerHTML='mail@fuze.pro'} else {document.getElementById('texty').innerHTML='8 912 77 20 444'}" onmouseout="if (document.getElementById('texty').innerHTML!='8 912 77 20 444') {document.getElementById('texty').innerHTML='8 912 77 20 444'} else {document.getElementById('texty').innerHTML='mail@fuze.pro'}">mail@fuze.pro</div>