javascript getelementbyid().className code example
Example 1: Javascript change element class
document.getElementById("myElementID").classList.add('myClassName');
document.getElementById("myElementID").classList.remove('myClassName');
Example 2: element.classname javascript
let el = document.getElementById('item');
if (el.className === 'active'){
el.className = 'inactive';
} else {
el.className = 'active';
}