var id_reg_prev = 0;

function city_by_reg_request( id_reg )
{
	if( id_reg == id_reg_prev ) return;
	id_reg_prev = id_reg;
	var select = document.getElementById("city_select");
	select.options.length = 0;
	select.options.add(document.createElement("OPTION"));
	select.options[0].value=0;
	select.options[0].innerText="Строим список городов...";
	select.disabled=true;
	var req = new Subsys_JsHttpRequest_Js();
	req.onreadystatechange = function()
	{
		if (req.readyState == 4)
		{
			select.options.length=0;
			if (req.responseJS)
			{
				select.options.add(document.createElement("OPTION"));
				select.options[0].value=0;
				select.options[0].innerText = "Выберите город...";
				for( var i=0; i<req.responseJS.length; i++ )
				{
					select.options.add(document.createElement("OPTION"));
					select.options[i+1].value=req.responseJS[i]["id"];
					select.options[i+1].innerText=req.responseJS[i]["name"]
				}
				select.disabled=false;
			}
			else
			{
				select.options.add(document.createElement("OPTION"));
				select.options[0].value=0;
				select.options[0].innerText = "Нет данных по региону";
				select.disabled=true;
			}
		}
	}
	req.caching = true;
	req.open('POST', 'inc/js_request.php?type=city_by_reg', true);
	req.send({ id_region: id_reg });
}