Removing a class on DOMContentLoaded

Created for answer to http://stackoverflow.com/questions/29868977/how-to-know-if-an-element-is-rendered

by UselessCode

HTML

<div id="box" class="offscreen"></div>

CSS

#box {
    height: 100px;
    width: 100px;
    border: #f00 solid 2px;
    transition: transform .5s;
}

.offscreen {
    transform: translatex(-100%);
}

JavaScript

var box = document.getElementById('box'),
    showBox = function (){
      box.classList.remove('offscreen');
    };
document.addEventListener("DOMContentLoaded", function(event) {
    window.requestAnimationFrame(showBox);
});