Have you suffered from the pain of debugging SharePoint Client Object Model (COM) in Javascript? If you haven’t.. I think you soon will.

The SP COM introduces lots of classes in Javascript. Although you can add some basic intellisense for VS for the SP COM (see http://msdn.microsoft.com/en-us/library/ff798328.aspx), you will quickly find that it is no where near good enough.

I found that being able to get the class name of a variable in Javascript helps when debugging. In IE8, you can do this with: myObj.constructor.__typeName.

For the code below for example, doing alert(appointments.constructor.__typeName) would tell me that it is of type “SP.ListItemCollection”, and doing alert(appointmentEnumerator.constructor.__typeName) would tell me that it is of type “SP.ArrayListEnumerator”. This also works for simple types such as Number and string.

function getAppointmentOnSucceeded(sender, args)
{
	var appointmentEnumerator = appointments.getEnumerator();

	while (appointmentEnumerator.moveNext())
	{
		var appointment = appointmentEnumerator.get_current();
		$get("appointmentDetails").innerHTML += "</br><b>" + appointment.get_item('Title') + "</b><br/>" + appointment.get_item('Description');
	}
}