//先準備 cityareas 的 data
//帶入城市、行政區兩個下拉選單的 id，即可關聯
function bind_city_area(select_city_id, select_area_id, refresh_now , area_not_selected, area_not_selected_term) {
  var cityObj = document.getElementById(select_city_id);
  var areaObj = document.getElementById(select_area_id);
  function on_city_change() {
    var cityIdx = cityObj.options[cityObj.selectedIndex].value;
    if(cityIdx != "all"){
	    areaObj.length = 0;
	    if(typeof area_not_selected != 'undefined') {
	      areaObj.length += 1;
        areaObj.options[areaObj.length - 1].value = "";
		    areaObj.options[areaObj.length - 1].text = (typeof area_not_selected_term != 'undefined' ? area_not_selected_term : "請選擇");
      }
	    for (var zipcode in cityareas[cityIdx]) {
				areaObj.length += 1;
				areaObj.options[areaObj.length - 1].value = zipcode;
				areaObj.options[areaObj.length - 1].text = cityareas[cityIdx][zipcode];
	    }
	  }else{
	  	$("#"+select_area_id).empty();
	  	$("#"+select_area_id).append('<option value="all">全部</otpion>');
	  }
  }
  document.getElementById(select_city_id).onchange = on_city_change;
  if (refresh_now) {
    on_city_change();
  }
}