[bes]

<button>click</button>
<script>
window.onload = function () {
	var mas = [0, 1, 2, 3];
	var len = mas.length ;
	var num = 0;
	var flag = true;
	document.body.children[0].onclick = function () {
		num++; 
		if (num > 3) {
			num = 3;
		}
		if (flag == true) {
			flag = false;
			setTimeout(function () {
				alert(mas[num]);
				num = 0;
				flag = true;
			}, 400);
		}
	}
}
</script>