JSFiddle - React, Tailwind, and code Playground

HTML

<form action="">
  1<input type="text" class="old">
  2<input type="text" class="old">
  <br>
  1*<input type="text" class="new">
  2*<input type="text" class="new">
</form>
<button id="upd">update</button>

JavaScript

let _old = document.querySelectorAll('.old'),
		_new = document.querySelectorAll('.new'),
    btn = document.querySelector('#upd');
btn.addEventListener('click', update);
function update(){
	_old.forEach((item,i)=>{
  	_new[i].value = item.value;
  })
}