javascript get element by id set class code example

Example 1: javascript change element class

//Overwrite all classes
element.className = "class";

//Add class
element.classList.add("class");

Example 2: element.classname javascript

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

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