document.element classname code example

Example 1: get elment by id within get element byclassname

var targetDiv = document.getElementById("foo").getElementsByClassName("bar")[0];
targetDiv.textContent = "Goodbye world!";

Example 2: element.classname javascript

let el = document.getElementById('item');

if (el.className === 'active'){
  el.className = 'inactive';
} else {
  el.className = 'active';
}