JSFiddle - React, Tailwind, and code Playground

HTML

<script>
    function fun1() {
    var number = parseInt(document.getElementById("itm1").value);
    if(number) {   
    document.getElementById("itm2").setAttribute('value', number*10);
    }
 }
    function fun2() {
    var number2 = parseInt(document.getElementById("itm2").value);
    if(number2) {   
    document.getElementById("itm1").setAttribute('value', number2/10);
    }
 }
</script>

<input id="itm1" onchange="fun1();" type="text" autocomplete="off" value="" />
<input id="itm2" onchange="fun2();" type="text" autocomplete="off" value="" />