script.js

let input = document.getElementById('inputBox');
let button = document.querySelectorAll('button');

let string = "";
let arr = Array.from(button); 
arr.forEach(button => {
    button.addEventListener('click', (e) =>{
        if(e.target.innerHTML == '=')
        {
            string=eval(string);
            input.value=string;
            
        }
        else if(e.target.innerHTML == 'AC') {
            string= "";
            input.value = string;
        }
        else if(e.target.innerHTML == 'DEL')
        {
            string=string.substring(0,string.length-1);
            input.value=string;
        }
        else{
            string += e.target.innerHTML;
            input.value = string;    
        }
        
    })
})