var inner_select   = 'Seleccione';
var value_select   = '00';
var loading_select = 'cargando';
var select_id	   = 'id';
var select_value   = 'nombre';

function getJson(uri,id,param)
{
	new Ajax.Request(
		uri,
		{
			method: 'POST',						
			parameters:
			{
				id: param
			},
			onLoading:
			function()
			{
				$(id).update('').disable();
				createOpt(id,value_select,loading_select);
			},
			onSuccess:
			function(json)
			{
				$(id).enable();
				json = json.responseText;
				getOpt(json.evalJSON(true),id);
			}
		});
}

function getOpt(json,id)
{
	$(id).update('');
	createOpt(id,value_select,inner_select);
	json.each(
		function(obj)
		{
			createOpt(id,obj[select_id],obj[select_value]);		
		}
	);
}

function createOpt(id,value,inner)
{
	var opt = document.createElement('option');
	opt.value = value;
	opt.innerHTML = inner;
	$(id).appendChild(opt);
}