Toggle an Element's Class

https://codepen.io/joe_bacal/pen/zdBvaG?editors=1111

html

<div class="box">Click Me</div>

css

.box {
  width:100px;
  height:100px;
  background-color:orange;
}

.blue {
  background-color:blue;
}

js

var box = document.querySelector('.box');

box.addEventListener('click', function(){
  switchIt();
});

function switchIt(){
  if (box.classList.contains('blue')){
    box.classList.remove('blue');
  } else {
    box.classList.add('blue');
  }
}