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 = eval(string);
            input.value = string;
        }
        else if (e.target.innerHTML === "AC") {
            string = "";
            input.value = string;
        }
        else if (e.target.innerHTML === "DEL") {
            string = string.slice(0, -1);
            input.value = string;
        }
        else {
            string += e.target.innerHTML;
            input.value = string;
        }
    });
});