[bes]

<button id="but">click</button>
<script>
(function () {
	var flag = true;
	but.onclick = function () {
		if (flag) { 
			console.log('click');
		}
		flag = false;
		setTimeout(function () {flag = true}, 500);
	}
	but.ondblclick = function () {
		console.log('dblclick');
	}
})();
</script>

http://learn.javascript.ru/events-and-timing-depth