JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id="input1" /><br />
<input type="text" id="input2" />
<button id="btnOK" onClick="mudarTexto();">
  OK
</button>

JavaScript

function mudarTexto() {
	document.getElementById("input2").value = document.getElementById("input1").value;
  document.getElementById("input1").value = "";
}