calculator.js

function calculate(operation) {
    const num1 = parseFloat(document.getElementById("num1").value);
    const num2 = parseFloat(document.getElementById("num2").value);
    let result;

    if (isNaN(num1) || isNaN(num2)) {
        result = 'Please enter valid numbers.';
    } else {
        switch (operation) {
            case 'add':
                result = num1 + num2;
                break;
            case 'subtract':
                result = num1 - num2;
                break;
            case 'multiply':
                result = num1 * num2;
                break;
            case 'divide':
                if (num2 === 0) {
                    result = 'Cannot divide by zero.';
                } else {
                    result = num1 / num2;
                }
                break;
            case 'modulo':
                result = num1 % num2;
                break;
            default:
                result = 'Invalid operation.';
        }
    }

    document.getElementById("result").innerHTML = 'Result: ' + result;
}