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

    })
}