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;
           }
    })
}