JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html>
<style>
table, th, td {
  border:1px solid black;
}
</style>
<body>

<h2>Tab 3</h2>

<table style="width:100%">
  <tr>
    <th>Year</th>
    <th>Outflow</th>
    <th>Inflow</th>
  </tr>
  <tr>
    <td>Year 0</td>
    <td><input type="text" id="out0"></td>
    <td><input type="text" id="in0"></td>
  </tr>
  <tr>
    <td>Year 1</td>
    <td><input type="text" id="out1"></td>
    <td><input type="text" id="in1"></td>
  </tr>
  <tr>
    <td>Year 2</td>
    <td><input type="text" id="out2"></td>
    <td><input type="text" id="in2"></td>
  </tr>
  <tr>
    <td>Year 3</td>
    <td><input type="text" id="out3"></td>
    <td><input type="text" id="in3"></td>
  </tr>
  <tr>
    <td>Year 4</td>
    <td><input type="text" id="out4"></td>
    <td><input type="text" id="in4"></td>
  </tr>
  <tr>
    <td>Year 5</td>
    <td><input type="text" id="out5"></td>
    <td><input type="text" id="in5"></td>
  </tr>
</table>

<br>
<form>
        Discount rate: <input type="text" id="dr">
        <br>
        Result: <input type="text" id="result">
        <br>
        <input type="button" value="NPV" onClick="npv()">
        <input type="button" value="IRR" onClick="irr()">
        <input type="button" value="PP" onClick="pp()">

</form>

</body>

JavaScript

function npv()
    {
        var in0, in1, in2, in3, in4, in5, out0, out1, out2, out3, out4, out5, dr, res;
        dr=parseFloat(document.getElementById('dr').value);
        in0=parseFloat(document.getElementById('in0').value);
        in1=parseFloat(document.getElementById('in1').value);
        in2=parseFloat(document.getElementById('in2').value);
        in3=parseFloat(document.getElementById('in3').value);
        in4=parseFloat(document.getElementById('in4').value);
        in5=parseFloat(document.getElementById('in5').value);
        out0=parseFloat(document.getElementById('out0').value);
        out1=parseFloat(document.getElementById('out1').value);
        out2=parseFloat(document.getElementById('out2').value);
        out3=parseFloat(document.getElementById('out3').value);
        out4=parseFloat(document.getElementById('out4').value);
        out5=parseFloat(document.getElementById('out5').value);
        res=(((in0-out0)/((1+(dr/100))**0))+((in1-out2)/((1+(dr/100))**1))+((in2-out2)/((1+(dr/100))**2))+((in3-out3)/((1+(dr/100))**3))+((in4-out4)/((1+(dr/100))**4))+((in5-out5)/((1+(dr/100))**5)));
        document.getElementById('result').value=res;
    }