JSFiddle - React, Tailwind, and code Playground
HTML
<script>
function copyThis(txObj) {
document.getElementById("copytpName").value = txObj.value;
}
</script>
<form>
<textarea id="tpName" name="tpName" onkeyup="copyThis(this);" style="margin-top: -9px; width: 275px; height: 40px;"></textarea>
</form>
<textarea id="copytpName" name="copytpName" style="margin-top: -9px; width: 275px; height: 40px;"></textarea>