scrpit.js

let displayValue = '';

function appendNumber(number) {
    displayValue += number;
    updateDisplay();
}

function appendOperator(operator) {
    if (displayValue === '') return;
    const lastChar = displayValue[displayValue.length - 1];
    if ('+-*/%'.includes(lastChar)) {
        displayValue = displayValue.slice(0, -1);
    }
    displayValue += operator;
    updateDisplay();
}

function appendDot() {
    if (displayValue === '' || /[+\-*/%]/.test(displayValue[displayValue.length - 1])) {
        displayValue += '0.';
    } else if (!displayValue.includes('.')) {
        displayValue += '.';
    }
    updateDisplay();
}

function clearDisplay() {
    displayValue = '';
    updateDisplay();
}

function deleteChar() {
    displayValue = displayValue.slice(0, -1);
    updateDisplay();
}

function calculate() {
    try {
        displayValue = eval(displayValue).toString();
    } catch {
        displayValue = 'Error';
    }
    updateDisplay();
}

function updateDisplay() {
    const display = document.getElementById('display');
    display.value = displayValue;
}