function checkAll() {
	errors = ''; 
	errors = checkLenght("voornaam", "2");
	errors = checkLenght("naam", "2");
	errors = checkLenght("bedrijf", "2");
	errors = checkLenght("onderwerp", "2");
	errors = checkLenght("bericht", "2");
	errors = checkEmail("email");

	if (errors == "") { 
		verzend();
	} else {
		alert("Please complete the form");
		return false;
	}
}

function checkAll_Boeken() {
	errors = ''; 
	errors = checkLenght("B_voornaam", "2");
	errors = checkLenght("B_naam", "2");
	errors = checkLenght("B_bedrijf", "2");
	errors = checkEmail("B_email");
	errors = checkValue('B_voorkeur');
	errors = checkValue('B_tarief');

	if (errors == "") { 
		verzend_boeken();
	} else {
		alert("Please complete the form");
		return false;
	}
}

function checkLenght(object, min){
	veld = document.getElementById(object);
	if (veld.value.length < min) {	
		document.getElementById(object).className = 'error';
		return 'error';
	} else {
		document.getElementById(object).className = 'ok';
	    return '';
	}
}

function checkValue(object){
	veld = document.getElementById(object);
	if (veld.value == "") {	
		document.getElementById(object).className = 'error';
		return 'error';
	} else {
		document.getElementById(object).className = 'ok';
	    return '';
	}
}

function checkEmail(object) {
	veld = document.getElementById(object).value;
	
	var at = "@";
	var dot = ".";
	var lat = veld.indexOf(at);
	var lstr = veld.length;
	var ldot = veld.indexOf(dot);
	
	if (veld.indexOf(at)==-1){
		document.getElementById(object).className = "error";
		return "error";
	} else if (veld.indexOf(at)==-1 || veld.indexOf(at)==0 || veld.indexOf(at)==lstr) {
		document.getElementById(object).className = "error";
		return "error";
	} else if (veld.indexOf(dot)==-1 || veld.indexOf(dot)==0 || veld.indexOf(dot)==lstr) {
		document.getElementById(object).className = "error";
		return "error";
	} else if (veld.indexOf(at,(lat+1))!=-1) {
		document.getElementById(object).className = "error";
		return "error";
	} else if (veld.substring(lat-1,lat)==dot || veld.substring(lat+1,lat+2)==dot) {
		document.getElementById(object).className = "error";
		return "error";
	} else if (veld.indexOf(dot,(lat+2))==-1) {
		document.getElementById(object).className = "error";
		return "error";
	} else if (veld.indexOf(" ")!=-1) {
		document.getElementById(object).className = "error";
		return "error";
	} else {
		document.getElementById(object).className = "ok";
		return "";	
	}	 
}