script.js

const display = document.querySelector('#display');

const buttons = document.querySelectorAll('button');

buttons.forEach((item)=>{
    item.onclick = () => {
        if(item.id == "clear"){
            display.innerText = "";
        }else if(item.id == "backspace"){
            let string = display.innerText.toString();
            display.innerText = string.substr(0, string.length - 1);
        } else if (display.innerText != "" && item.id=="equal"){
            display.innerText = eval (display.innerText);
        } else if(display.innerText == "" && item.id== "equal"){
            display.innerText = "Null";
            setTimeout(() => (display.innerText = ""), 2000);
        } else{
            display.innerText += item.id;
        }
    }
});

const themeToggleBtn = document.querySelector('.theme-toggler');

const calculator = document.querySelector('.calculator');

let isDark = true;

themeToggleBtn.onclick = () => {
    calculator.classList.toggle("dark");

    themeToggleBtn.classList.toggle("active");

    isDark = !isDark;
};