JSFiddle - React, Tailwind, and code Playground

HTML

<script>
function net_cash() 
{
var cash = 0;
var retained = document.getElementById("cash_retained");
var change = document.getElementById("cash_change");

cash += parseInt(retained.value);
cash += parseInt(change.value);

if (isNaN(cash))
{
    document.getElementById("net_cash").value = "0";
}
else
{
    document.getElementById("net_cash").value = cash;
}
}
</script>

<td><input type="text" value="" id="cash_retained" name="cash_retained" onkeyup="net_cash()" size="25"></td>
<td><input type="text" value="" id="cash_change" name="cash_change" onkeyup="net_cash()" size="25"></td>
<td><input type="text" value="0" id="net_cash" name="net_cash"></td>