js 如何控制文本域输入内容在一定间隔时间段才触发事件查询相关数据

<script>
var flag = 0;
var t;
function openFlag () {
	t = setTimeout(function(){flag = 1; dosomething();}, 1000);
}
function closeFlag() {
	clearTimeout(t);
	flag = 0;
}
function dosomething() {
	if (flag) {
		// do something
		alert('aaa');
	}
}
</script>

<input type="text"  onkeydown="openFlag()" onkeyup="closeFlag()" />