text: let screen = document.getElementById('screen');
  buttons = document.querySelectorAll('button');
  let screenValue = '';
  for (item of buttons) {
      item.addEventListener('click', (e) => {
          buttonText = e.target.innerText;
          console.log('Button text is ', buttonText);
          if (buttonText == 'X') {
              buttonText = '*';
              screenValue += buttonText;
              screen.value = screenValue;
          } else if (buttonText == 'C') {
              screenValue = "";
              screen.value = screenValue;
          } else if (buttonText == '=') {
              screen.value = eval(screenValue);
  
          } else if (buttonText == "CE") {
              screenValue = screen.value.substr(0, screen.value.length - 1);
              screen.value = screenValue;
          } else {
              screenValue += buttonText;
              screen.value = screenValue;
          }
      })
  }