window.onload = prepForm;

function prepForm() {
	for (var i=0; i<document.forms.length; i++) {
		var thisform = document.forms[i];
		thisform.onsubmit = function() {
			return validate(this);
		}
	}
}

function validate(app) {
	for (var i=0; i<app.elements.length; i++) {
		var element = app.elements[i];
		if (element.className.indexOf("required") != -1) {
			if (!isFilled(element)) {
				alert ("You forgot to fill in your "+element.name+"!");
				return false;
			}
		}
		if (element.className.indexOf("email") != -1) {
			if (!isEmail(element)) {
				alert ("Please make sure that the E-mail address you entered is valid!");
				return false;

			}
		}
	}
	return true;
}


function isFilled(field) {
	if (field.value.length < 1) {
		return false; }
	else {return true; }
}

function isEmail(field) {
	if (field.value.indexOf("@") == -1 || field.value.indexOf(".") == -1) {
		return false;}
	else {return true; }
}