index.js

console.log("Hello world")

let count = 0;
let counterDisplay = document.getElementById('counter')


function increase() {
    count++;
    // console.log(count);
    counterDisplay.innerText = count;
}

function decrease() {
    count--;
    counterDisplay.innerText = count;   
    // console.log(count);
}

function reset() {
    count = 0;
    counterDisplay.innerHTML = `<mark>${count}</mark>`;
    // console.log(count);
}

function selectTheme (theme) {
    document.getElementsByTagName('body')[0].className = theme
    document.getElementsByTagName('main')[0].className = theme
    
    let buttons = document.getElementsByTagName('button')

    for (let i = 0; i < buttons.length; i++) {
        buttons[i].className = theme;
    }

}