JavaScript: Detects what mouse button was used, left, right, middle, or middle scroll either direction

script.js

/**
   Better Javascript Mouse Events
   Author: Casey Childers
   https://jsfiddle.net/BNefn/
**/
(function(){
		// use addEvent cross-browser shim: https://gist.github.com/dciccale/5394590/
    var addEvent = function(a,b,c){try{a.addEventListener(b,c,!1)}catch(d){a.attachEvent('on'+b,c)}};
    
    /* This function detects what mouse button was used, left, right, middle, or middle scroll either direction */
    function GetMouseButton(e) {
        e = window.event || e; // Normalize event variable
        
        var button = '';
        if (e.type == 'mousedown' || e.type == 'click' || e.type == 'contextmenu' || e.type == 'mouseup') {
            if (e.which == null) {
                button = (e.button < 2) ? "left" : ((e.button == 4) ? "middle" : "right");
            } else {
                button = (e.which < 2) ? "left" : ((e.which == 2) ? "middle" : "right");
            }
        } else {
            var direction = e.detail ? e.detail * (-120) : e.wheelDelta;
            switch (direction) {
                case 120:
                case 240:
                case 360:
                    button = "up";
                    break;
                case -120:
                case -240:
                case -360:
                    button = "down";
                    break;
            }
        }
        
        var type = e.type
        if(e.type == 'contextmenu') {type = "click";}
        if(e.type == 'DOMMouseScroll') {type = "mousewheel";}

				switch(button) {
            case 'contextmenu':
        		case 'left':
            case 'middle':
            case 'up':
            case 'down':
            case 'right':
            
                if (document.createEvent) {
                  event = new Event(type+':'+button);
                  e.target.dispatchEvent(event);
                } else {
                  event = document.createEventObject();
                  e.target.fireEvent('on'+type+':'+button, event);
                }
                
            break;
        }
    }

 		addEvent(window, 'mousedown', GetMouseButton);
    addEvent(window, 'mouseup', GetMouseButton);
    addEvent(window, 'click', GetMouseButton);
    addEvent(window, 'contextmenu', GetMouseButton);
 
    /* One of FireFox's browser versions doesn't recognize mousewheel, we account for that in this line */
		var MouseWheelEvent = (/Firefox/i.test(navigator.userAgent)) ? "DOMMouseScroll" : "mousewheel";
    addEvent(window, MouseWheelEvent, GetMouseButton);
})();


/* Better Mouse Click Events Example (uses jquery for simplicity, but the above will work cross browser and file the same event names, IE uses on before the names) */
$('#Test').on('mouseup',function(e){$(this).append(e.type+'<br />');})
					.on('mouseup:left',function(e){$(this).append(e.type+'<br />');})
					.on('mouseup:middle',function(e){$(this).append(e.type+'<br />');})
					.on('mouseup:right',function(e){$(this).append(e.type+'<br />');})
          
          .on('click',function(e){$(this).append(e.type+'<br />');})
          .on('click:left',function(e){$(this).append(e.type+'<br />');})
					.on('click:middle',function(e){$(this).append(e.type+'<br />');})
					.on('click:right',function(e){$(this).append(e.type+'<br />');})
          
          .on('mousedown',function(e){$(this).html('').append(e.type+'<br />');})
          .on('mousedown:left',function(e){$(this).append(e.type+'<br />');})
					.on('mousedown:middle',function(e){$(this).append(e.type+'<br />');})
					.on('mousedown:right',function(e){$(this).append(e.type+'<br />');})
					
          .on('mousewheel',function(e){$(this).append(e.type+'<br />');})
          .on('mousewheel:up',function(e){$(this).append(e.type+'<br />');})
					.on('mousewheel:down',function(e){$(this).append(e.type+'<br />');})
          ;