script.js

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

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