/**
 * Checks the fields of a form on non-emptiness.
 * Usage: checkForm(formName, field1Name, field2Name, ...)
 */
function checkForm() 
{
	var sFormName = arguments[0];
	
	for (var i = 1; i < arguments.length; i++)
	{
		sField = arguments[i];

		oElement = eval("document." + sFormName + "." + sField);

		if (oElement)
		{
			if (oElement.length != undefined)
			{
				bOk = false;
				for (j = 0; j < oElement.length; j++)
				{
					if (oElement[j].checked)
					{
						bOk = true;
					}
				}
				
				if (!bOk)
				{
					alert("Sommige verplichte velden zijn nog niet ingevuld.");
					oElement[0].focus();
					return false;
				}
			}
			else if (oElement.value == "")
			{
				alert("Sommige verplichte velden zijn nog niet ingevuld.");
				oElement.focus();
				return false;
			}
		}
	}
	
	return true;
}

/**
 * Checks the fields of a form on non-emptiness.
 * Usage: checkForm(formName, field1Name, field1RegEx, field1Alert, field2Name, field2RegEx, field2Alert, ...)
 */
function checkFormRegEx()
{
	var sFormName = arguments[0];
	
	for (var i = 1; i < arguments.length; i += 3)
	{
		sField = arguments[i];
		sRegEx = arguments[i + 1];
		sAlert = arguments[i + 2];
		
		if (oElement = eval("document." + sFormName + "." + sField))
		{
			oRegEx = new RegExp(sRegEx);
			if (!oRegEx.test(oElement.value))
			{
				alert(sAlert);
				oElement.focus();
				return false;
			}
		}
	}

	return true;
}