用jsp完成购物简易计算器

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        img{
            width: 50px;
            height: 40px;
        }
    </style>
</head>
<body>
    <table>
        <tr>
            <td><img src="img/cart.png"></td>
            <td colspan="3">购物简易计算器</td>
        </tr>
        <tr>
            <td>第一个数</td>
            <td colspan="3" ><input type="text" ></td>
        </tr>
        <tr>
            <td>第二个数</td>
            <td colspan="3"><input type="text" ></td>
        </tr>
        <tr>
            <td><button onclick="cal('+')">+</button></td>
            <td><button onclick="cal('-')">-</button></td>
            <td><button onclick="cal('*')">*</button></td>
            <td><button onclick="cal('/')">/</button></td>
        </tr>
        <tr>
            <td>计算结果</td>
            <td colspan="3"><input type="text" id="result"></td>
        </tr>
    </table>
    <script>
        function cal(type) {
            var num1 = document.getElementsByTagName('input')[0].value;
            var num2 = document.getElementsByTagName('input')[1].value;
            var result = eval(parseInt(num1) + type + parseInt(num2));
            document.getElementById('result').value = result;
        }
    </script>
</body>
</html>