script.js

let displayValue = '';
const maxInputLength = 20;

function clearDisplay() {
  displayValue = '';
  updateDisplay('0');
}

function appendNumber(number) {
  if (displayValue.length < maxInputLength) {
    displayValue += number;
    updateDisplay(displayValue);
  }
}

function appendOperator(operator) {
  if (displayValue.length < maxInputLength) {
    displayValue += operator;
    updateDisplay(displayValue);
  }
}

function calculate() {
  try {
    const result = math.evaluate(displayValue);
    displayValue = result.toString();
    if (displayValue.length > maxInputLength) {
      displayValue = parseFloat(displayValue).toExponential(10);
    }
    updateDisplay(displayValue);
  } catch (error) {
    updateDisplay('Error');
    displayValue = '';
  }
}

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

document.addEventListener('keydown', (event) => {
  const key = event.key;
  if (!isNaN(key) || key === '.') {
    appendNumber(key);
  } else if (['+', '-', '*', '/'].includes(key)) {
    appendOperator(key);
  } else if (key === 'Enter') {
    event.preventDefault();
    calculate();
  } else if (key === 'Backspace') {
    displayValue = displayValue.slice(0, -1);
    updateDisplay(displayValue || '0');
  } else if (key === 'Escape') {
    clearDisplay();
  }
});