All events have properties just like the keyboard ones.  You can look up what properties there should be for each type of event but different browsers may not support all of them.  Instead you can find out yourself what your particular browser does support. 

Create a new blank page called eventproperties.html.  Put his code inside it (delete any other HTML/CSS/JavaScript):

<!DOCTYPE html>
        <meta charset="UTF-8">
        <script type="text/javascript">
            function showProperties(e) {
	    	var o = e;
	    	for (att in o) {
	    	    var newElement=document.createElement('p');
	    	    if (document.body.textContent){
	    	        newElement.textContent='Property: '+att+' Value: '+o[att];
	    	    } else {
	    	        newElement.innerText='Property: '+att+' Value: '+o[att];
    <body onkeydown="showProperties(event);">
	<p onmouseup="showProperties(event);">Click me to see properties (or press a key).</p>	

Save and try and you will see a list of all available properties for mouse presses or key presses.  Don't worry about the above code as that is just there to show the properties.

You can find the properties of any event this way.  Try adding an event trigger for onload.  You could also add one for onscroll but you will also need to add some extra content so that scrolling is possible (and the list of properties appears below that content and each time you scroll to get to it more copies of the properties are added!).