Global Event Handler (GEH) Class

Global Event Handler (GEH) class is designed to solve a practical problem in JavaScript. If you want to assign more than one event handlers to a JavaScript event, there is a problem of resource sharing. With the GEH class, multiple event handler codes can be assigned to a single JavaScript event.

GEH: GEH Class.
GEH.NewHandler method: Add a new event handler code to the event associated with this GEH object.
GEH.RemoveHandler Method: Removes a previously installed event handler code to the event associated with this GEH object.
GEH.CallHandlers Method: Evaluates all of the installed event handler codes, once.
GEH.tasks Property: Container array for the event handler codes installed.

Pre-declared GEH Objects

API defines some pre-declared GEH objects that are associated to some JavaScript object events for the users convenience.

gehMMove GEH Object: Associated with document.onmousemove event.
gehResize GEH Object: Associated with window.onresize event.
gehScroll GEH Object: Associated with window.onscroll event.

	GEH Class
Definition:	Returns a new GEH object.
Syntax:	`new GEH () ;`
Arguments:	None
Returns:	A new GEH object.
Remarks:	GEH class is designed to handle multiple event handlers for a single event.
Example:	// Create a new GEH object var gehMMove = new GEH() ; // Access the CallHandlers method of gehMMove from this dummy global function function gehMMoveHandler (ev) { gehMMove.CallHandlers(ev) ; } // Assign the dummy function to the document.onmousemove event document.onmousemove = gehMMoveHandler ; // Add a new handler to call to whenever a mouse is moved gehMMove.NewHandler ("mouseEventHandler (ev)") ;

	GEH.NewHandler Method
Definition:	Add a new event handler code to the event associated with this GEH object.
Syntax:	`function GEH.NewHandler(str) ;`
Arguments:	str: String value containing a call to a function or any JavaScript code to be evaluated whenever the associated event occurs.
Returns:	The index of the event handler. Use this index to remove the event handler later via RemoveHandler method.
Remarks:	The code in 'str' can reference an event object named 'ev', though, the properties of the 'ev' object depends on the browser used.
Example:	// Create a new GEH object var gehMMove = new GEH() ; // Access the CallHandlers method of gehMMove from this dummy global function function gehMMoveHandler (ev) { gehMMove.CallHandlers(ev) ; } // Assign the dummy function to the document.onmousemove event document.onmousemove = gehMMoveHandler ; // Add a new handler to call to whenever a mouse is moved gehMMove.NewHandler ("mouseEventHandler (ev)") ;

	GEH.RemoveHandler Method
Definition:	Removes a previously installed event handler code to the event associated with this GEH object.
Syntax:	`function GEH.RemoveHandler(index) ;`
Arguments:	index: Handler index as returned by GEH.NewHandler method.
Returns:	None.
Remarks:	None
Example:	// Create a new GEH object var gehMMove = new GEH() ; var handlerIndex = gehMMove.NewHandler ("mouseEventHandler (ev)") ; ... gehMMove.RemoveHandler(handlerIndex) ;

	GEH.CallHandlers Method
Definition:	Evaluates all of the installed event handler codes, once.
Syntax:	`function GEH.CallHandlers(ev) ;`
Arguments:	ev: Event object passed by some browsers as event handler argument.
Returns:	None
Remarks:	This method makes an event object named 'ev' to be available for all handler codes. That is, the installed (via GEH.NewHandler method) event handler codes can reference to this 'ev' object. Note that, this 'ev' object is enhanced version of the argument 'ev' to cover more browsers, though, the properties of the 'ev' object depends on the browser used. In order to use this method as an event handler of an event, you need to create a wrap-around function as shown in the example below, since only global functions can be used as event handlers.
Example:	// window.onresize Global Event Handler var gehResize = new GEH() ; // This is the dummy wrap-around global function function gehResizeHandler (ev) { gehResize.CallHandlers(ev) ; } // Assing the dummy function as event handler window.onresize = gehResizeHandler ;

	GEH.tasks Property
Definition:	Container array for the event handler codes installed.
Remarks:	Normally, you do not access this array. Instead use GEH.NewHandler and GEH.RemoveHandler methods.

	gehMMove GEH Object
Definition:	Associated with document.onmousemove event.
Syntax:	`var gehMMove = new GEH() ; function gehMMoveHandler (ev) { gehMMove.CallHandlers(ev) ; } document.onmousemove = gehMMoveHandler ; gehMMove.NewHandler ("mouseEventHandler (ev)") ;`
Remarks:	Add new handlers to document.onmousemove event by calling gehMMove.NewHandler() method.
Example:	// Show the position of mouse pointer in the status bar of the window. gehMMove.NewHandler ("window.status = MouseX + \", \" + MouseY ;") ;

	gehResize GEH Object
Definition:	Associated with window.onresize event.
Syntax:	`var gehResize = new GEH() ; function gehResizeHandler (ev) { gehResize.CallHandlers(ev) ; } window.onresize = gehResizeHandler ;`
Remarks:	Add new handlers to window.onresize event by calling gehResize.NewHandler() method.
Example:	// Show the client area width and height on the status bar of the window. gehResize.NewHandler ("window.status = windWidth() + \", \" + windHeight() ;") ;

	gehScroll GEH Object
Definition:	Associated with window.onscroll event
Syntax:	`var gehScroll = new GEH() ; function gehScrollHandler (ev) { gehScroll.CallHandlers(ev) ; } window.onscroll = gehScrollHandler ;`
Remarks:	Add new handlers to window.onscroll event by calling gehScroll.NewHandler() method.
Example:	// Show the document horizontal and vertical scroll offset // on the status bar of the window. gehScroll.NewHandler ("window.status = docXScroll() + \", \" + docYScroll() ;") ;