index.js

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 = ''
        }
        
        else if (buttonText == '='){
            screen.value = eval(screenValue);
            screenValue = screen.value
           

        }

        else{
            
            screenValue += buttonText
            screen.value = screenValue
        }
    })
}