archive uploader date field autoNext

function numberpress(keycode) /* checks whether last pressed key is a number so it goes to the next field only then */ {
	if(keycode >= 48 && keycode <= 57) /* number row */ return true;
	if(keycode >= 96 && keycode <= 105) /* num pad */ return true;
		else return false;
}

date_year.addEventListener("keyup", function(key){if (date_year.value.length == 4 && numberpress(key.keyCode) ) { date_month.focus(); } } );
date_month.addEventListener("keyup", function(key){if (date_month.value.length == 2 && numberpress(key.keyCode) ) { date_day.focus(); } } );