<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()" />