Aim: A simple calculator web application that takes two numbers and an operator (+, -, /, * and %) from an HTML page and returns the result page with the operation performed on the operands.

HTML Calculator


<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>HTML Calculator</title>
    <style>
        body {
            background-color: black;
            color: gold;
            font-family: Arial, sans-serif;
            display: flex;
            justify-content: center;
            align-items: center;
            height: 100vh;
        }
        .calculator {
            width: 260px;
            padding: 15px;
            border: 2px solid gold;
            border-radius: 10px;
            background-color: black;
            text-align: center;
        }
        .display {
            width: 100%;
            height: 50px;
            text-align: right;
            font-size: 24px;
            margin-bottom: 10px;
            background-color: #222;
            color: gold;
            border: none;
            padding-right: 10px;
        }
        .buttons {
            display: grid;
            grid-template-columns: repeat(4, 1fr);
            gap: 5px;
        }
        button {
            width: 100%;
            height: 50px;
            font-size: 18px;
            cursor: pointer;
            background-color: gold;
            border: none;
            color: black;
            font-weight: bold;
            border-radius: 5px;
        }
        button:hover {
            background-color: orange;
        }
        .double {
            grid-column: span 2;
        }
        .operator {
            background-color: darkorange;
        }
        .operator:hover {
            background-color: orangered;
        }
    </style>
</head>
<body>

<div class="calculator">
    <input type="text" id="display" class="display" readonly>
    <div class="buttons">
        <button onclick="clearDisplay()">C</button>
        <button onclick="addToDisplay('%')">%</button>
        <button onclick="addToDisplay('/')">/</button>
        <button class="operator" onclick="addToDisplay('*')">×</button>

        <button onclick="addToDisplay('7')">7</button>
        <button onclick="addToDisplay('8')">8</button>
        <button onclick="addToDisplay('9')">9</button>
        <button class="operator" onclick="addToDisplay('-')">−</button>

        <button onclick="addToDisplay('4')">4</button>
        <button onclick="addToDisplay('5')">5</button>
        <button onclick="addToDisplay('6')">6</button>
        <button class="operator" onclick="addToDisplay('+')">+</button>

        <button onclick="addToDisplay('1')">1</button>
        <button onclick="addToDisplay('2')">2</button>
        <button onclick="addToDisplay('3')">3</button>
        <button class="operator" onclick="calculateResult()">=</button>

        <button class="double" onclick="addToDisplay('0')">0</button>
        <button onclick="addToDisplay('.')">.</button>
    </div>
</div>

<script>
    function addToDisplay(value) {
        document.getElementById("display").value += value;
    }

    function calculateResult() {
        try {
            document.getElementById("display").value = new Function('return ' + document.getElementById("display").value)();
        } catch {
            document.getElementById("display").value = "Error";
        }
    }

    function clearDisplay() {
        document.getElementById("display").value = "";
    }
</script>

</body>
</html>
Output:

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