Button select random from array

gistfile1.txt

//Vanilla
button = document.getElementsByTagName('button')[0];
button.addEventListener('click', function(){
   rotate();
});

var rotate = function(){
   var sides = ['show-front', 'show-back', 'show-left', 'show-right', 'show-top', 'show-bottom'];
   var side = sides[Math.floor(Math.random()*sides.length)];
   
   for(var i in sides){
      boxes = document.getElementsByClassName('box');
      for(var o = 0; o < boxes.length; o++){
         boxes[o].classList.remove(sides[i]);
         boxes[o].classList.add(side);
      }
   }
}


//JQuery
$('button').on('click', function(){
   rotate();
});

var rotate = function(){
   //Array
   var sides = ['show-front', 'show-back', 'show-left', 'show-right', 'show-top', 'show-bottom'];
   //Select
   var side = sides[Math.floor(Math.random()*sides.length)];
   //Apply
   var box = document.getElementByClassName('box');
   $('.box').removeClass('show-front show-back show-left show-right show-top show-bottom').addClass(side);
}