JSFiddle - React, Tailwind, and code Playground

HTML

<script>
    
function hideLabel(fieldname) {
    document.getElementById(fieldname).label.style.visibility = 'hidden';
}
</script>

<label for='useremail'>Registered email address</label>
<input type='text' value='' name='useremail'
onfocus='hideLabel("useremail");' id='useremail' class='useremail'>

JavaScript

var labels = document.getElementsByTagName('LABEL');
for (var i = 0; i < labels.length; i++) {
    if (labels[i].htmlFor != '') {
        var elem = document.getElementById(labels[i].htmlFor);
        if (elem) elem.label = labels[i];
    }
}