function addEvent (el, ev, fn) {
	if (window.addEventListener) {
		el.addEventListener(ev, fn, true);
		return true;
	} else if (window.attachEvent) {
		var r = el.attachEvent("on" + ev, fn);
		return r;
	} else {
		el["on" + ev] = fn;
	}
}


function init() {
	//startShowWords();
	var inputs = document.getElementsByTagName("input");
	for (var i = 0; i < inputs.length; i++) {
		var el = inputs[i];
		addEvent(el, "blur", checkForm)
	}
}

function checkForm() {
	var enabled = false;
	var inputs = document.getElementsByTagName("input");
	for (var i = 0; i < inputs.length; i++) {
		var el = inputs[i];
		if (el.value == "") {
			return;
		}
	}
	enabled = true;
	if (enabled == true) {
		enableForm(1);
	} else {
		enableForm(0);
	}
	
}
function enableForm(b) {
	var btn = document.getElementById("submit");
	if (b == 1) {
		btn.disabled = false;
	} else {
		btn.disabled = true;
	}
}
function startShowWords() {
	var ban = document.getElementById("bottom");
	ban.innerHTML = woorden[startWoord];
//	alert(ban.style.backgroundColor);
	if (startWoord > aantal - 1) {
		startWoord = 0;
	}
	startWoord ++;
	//setInterval(startShowWords, 5000);
}


addEvent(window,"load", init);