function formValidator(){
	
	
	var an = document.getElementById('an');
	var em = document.getElementById('em');
	var tf = document.getElementById('tf');
	
	
	if(isAlphabet(an, "Vul uw naam in")){
	if(emailValidator(em, "Vul een geldig E-mail adres in")){
	if(isNumeric(tf, "Vul uw telefoonnummer in (enkel cijfers)")){

						return true;
	} } }
	
	return false;
	
}

function notEmpty(elem, helperMsg){
	if(elem.value.length == 0){
		alert(helperMsg);
		elem.focus();
		return false;
	}
	return true;
}

function isNumeric(elem, helperMsg){
	var numericExpression = /^[0-9]+$/;
	if(elem.value.match(numericExpression)){
		return true;
	}else{
		alert(helperMsg);
		elem.focus();
		return false;
	}
}

function isAlphabet(elem, helperMsg){
	var alphaExp = /^[a-zA-Z]+$/;
	if(elem.value.match(alphaExp)){
		return true;
	}else{
		alert(helperMsg);
		elem.focus();
		return false;
	}
}

function isAlphanumeric(elem, helperMsg){
	var alphaExp = /^[0-9a-zA-Z]+$/;
	if(elem.value.match(alphaExp)){
		return true;
	}else{
		alert(helperMsg);
		elem.focus();
		return false;
	}
}

function lengthRestriction(elem, min, max){
	var uInput = elem.value;
	if(uInput.length >= min && uInput.length <= max){
		return true;
	}else{
		alert("Een telefoonnummer dient 10 cijfers te bevatten");
		elem.focus();
		return false;
	}
}

function madeSelection(elem, helperMsg){
	if(elem.value == "Kies"){
		alert(helperMsg);
		elem.focus();
		return false;
	}else{
		return true;
	}
}

function emailValidator(elem, helperMsg){
	var emailExp = /^[\w\-\.\+]+\@[a-zA-Z0-9\.\-]+\.[a-zA-z0-9]{2,4}$/;
	if(elem.value.match(emailExp)){
		return true;
	}else{
		alert(helperMsg);
		elem.focus();
		return false;
	}
}