function isEmpty(str_naam, str_partner) {

str_naam = document.forms[0].naam.value 
str_email = document.forms[0].email.value 
str_partner = document.forms[0].partner.value

  //name veld
	if (str_naam == "" || str_naam == null || !isNaN(str_naam) || str_naam.charAt(0) == ' ') {
		alert("\"naam-veld\" is niet geldig.")
		return false;
		}

  //e-ail veld 

     if (str_email == "" || str_email == null || !isNaN(str_email) || str_email.charAt(0) == ' ') {
		alert("\"e-mail\" is niet geldig.")
		return false;
		}
		
  //partner veld 

     if (str_partner == "" || str_partner == null || !isNaN(str_partner) || str_partner.charAt(0) == ' ') {
		alert("\"partnernaam\" is niet geldig.")
		return false;
		}
	
	return true
	}


//function to check valid email address

function isValidEmail(strEmail){

  validRegExp = /^[^@]+@[^@]+.[a-z]{2,}$/i;

  strEmail = document.forms[0].email.value;

 // search email text for regular exp matches

    if (str_email.search(validRegExp) == -1) 
	{
	alert('A valid e-mail address is required.\nPlease amend and retry');
	return false;
	} 
	return true; 
	}

//function that performs all functions, defined in the onsubmit event handler
function check(form){
if (isEmpty(form.naam)){
  if (isEmpty(form.partner)){
   	if (isValidEmail(form.email)){
		  return true;
		}
	  
  }
}
return false;
}