JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html lang="sl">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Izračun izenačenja glavnice</title>
    <style>
        body {
            font-family: Arial, sans-serif;
            margin: 20px;
        }
        table, th, td {
            border: 1px solid black;
            border-collapse: collapse;
            padding: 8px;
            text-align: center;
        }
        th, td {
            width: 150px;
        }
    </style>
</head>
<body>
    <h1>Izračun izenačenja glavnice</h1>
    <form id="calcForm">
        <label for="rate1">Obrestna mera 1 (%):</label>
        <input type="number" id="rate1" name="rate1" step="0.1" value="1.7" required><br><br>
        <label for="rate2">Obrestna mera 2 (%):</label>
        <input type="number" id="rate2" name="rate2" step="0.1" value="3.0" required><br><br>
        <label for="membershipFee1">Članarina 1 (EUR):</label>
        <input type="number" id="membershipFee1" name="membershipFee1" step="0.01" value="0.00" required><br><br>
        <label for="membershipFee2">Članarina 2 (EUR):</label>
        <input type="number" id="membershipFee2" name="membershipFee2" step="0.01" value="162.00" required><br><br>
        <button type="button" onclick="calculatePrincipal()">Izračunaj</button>
    </form>

    <h2>Rezultati</h2>
    <table id="resultTable">
        <thead>
            <tr>
                <th>Glavnica (EUR)</th>
                <th id="principal"></th>
            </tr>
        </thead>
    </table>

    <script>
        function calculatePrincipal() {
            let rate1 = parseFloat(document.getElementById('rate1').value) / 100;
            let rate2 = parseFloat(document.getElementById('rate2').value) / 100;
            let membershipFee1 = parseFloat(document.getElementById('membershipFee1').value);
            let membershipFee2 = parseFloat(document.getElementById('membershipFee2').value);

            let...