javascript set classname code example

Example 1: js add class

var element = document.getElementById('element');
element.classList.add('class-1');
element.classList.add('class-2', 'class-3');
element.classList.remove('class-3');

Example 2: javascript change element class

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

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

Example 3: element.classname javascript

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

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