function hideOnly(targetID) {
	var elementmode = document.getElementById(targetID).style;
	elementmode.display = 'none';
}

function showOnly(targetID) {
	var elementmode = document.getElementById(targetID).style;
	elementmode.display = '';
}

function showhide(targetID) {
	//change target element mode
	var elementmode = document.getElementById(targetID).style;
	elementmode.display = (!elementmode.display) ? 'none' : '';
	return elementmode.display;
}

function changetext(changee,oldText,newText) {
	//changes text in source element
	var elementToChange = document.getElementById(changee);
	elementToChange.innerHTML = (elementToChange.innerHTML == oldText) ? newText : oldText;
}

function forceChangeText(changee,oldText) {
	var elementToChange = document.getElementById(changee);
	elementToChange.innerHTML = oldText;	
}

function workforchange(targetID,sourceID,oldContent,newContent) {
	var hidden = showhide(targetID);
	changetext(sourceID,oldContent,newContent);
}

function eitherOr (targetID1,sourceID1,oldContent1,newContent1,targetID2,sourceID2,oldContent2) {

// if show one, make sure other is hidden -  call to showhide returns status
	var hidden = showhide(targetID1);
	changetext(sourceID1,oldContent1,newContent1);
	
	if (!hidden) {
		hideOnly(targetID2);
		forceChangeText(sourceID2,oldContent2);
	}

}

function onlyThis (targetID1,sourceID1,content1,targetID2,sourceID2,content2) {

	// only show targetid1
	showOnly(targetID1);
	forceChangeText(sourceID1,content1);
	
	hideOnly(targetID2);
	forceChangeText(sourceID2,content2);

}


// Cruft note: The content of "oldContent," the third argument of the
// workforchange() function, must match the existing content of the changer text.

/*
<a href="javascript:workforchange('loginFormWrapper','login_changer','LOGIN','HIDE LOGIN');" 
id='login_changer'>LOGIN</a> | <a 
href="javascript:workforchange('registrationFormWrapper','registration_changer','REGISTER','HIDE REGISTRATION');"
id='registration_changer'>REGISTER</a>

becomes

<a href="javascript:eitherOr('loginFormWrapper','login_changer','LOGIN','HIDE LOGIN','registrationFormWrapper','registration_changer','REGISTER');" 
id='login_changer'>LOGIN</a> | <a 
href="javascript:eitherOr('registrationFormWrapper','registration_changer','REGISTER','HIDE REGISTRATION','loginFormWrapper','login_changer','LOGIN');"
id='registration_changer'>REGISTER</a>


*/