professional_javascript_for_web/ch22/DragAndDropExample02.htm

<!DOCTYPE html>
<html>
<head>
    <title>Drag and Drop Example</title>
    <script type="text/javascript" src="EventUtil.js"></script>
</head>
<body>
    <div id="myDiv1" class="draggable" style="background:red;width:100px;height:100px;position:absolute"></div>
    <div id="myDiv2" class="draggable" style="background:blue;width:100px;height:100px;position:absolute;left:100px"></div>
    <script type="text/javascript">
    
        var DragDrop = function(){
        
            var dragging = null;
            
            function handleEvent(event){
            
                //get event and target
                event = EventUtil.getEvent(event);
                var target = EventUtil.getTarget(event);            
            
                //determine the type of event
                switch(event.type){
                    case "mousedown":
                        if (target.className.indexOf("draggable") > -1){
                            dragging = target;
                        }                     
                        break;
                        
                    case "mousemove":
                        if (dragging !== null){
                            
                            //assign location
                            dragging.style.left = event.clientX + "px";
                            dragging.style.top = event.clientY + "px";                    
                        }                    
                        break;
                        
                    case "mouseup":
                        dragging = null;
                        break;
                }
            };
            
            //public interface
            return {            
                enable: function(){
                    EventUtil.addHandler(document, "mousedown", handleEvent);
                    EventUtil.addHandler(document, "mousemove", handleEvent);
                    EventUtil.addHandler(document, "mouseup", handleEvent);
                },
                
                disable: function(){
                    EventUtil.removeHandler(document, "mousedown", handleEvent);
                    EventUtil.removeHandler(document, "mousemove", handleEvent);
                    EventUtil.removeHandler(document, "mouseup", handleEvent);
                }
            }
        }();
        
        DragDrop.enable();
                        

        
    </script>
</body>
</html>