What is the difference between window.onload() and document.addEventListener('load', ..)?
<p>It seems to me that both events are fired when every resource and its dependent resources have finished loading. This rises some questions:</p>

<ol>
<li>Is there any difference between those events?</li>
<li>Which event gets fired first?</li>
<li>Which event could or should be preferred for adding an additional HTML element to the body after everything has been finished loading?</li>
</ol>