var xmlHttp;
var optionType;


function createXMLHttpRequest()
{
	//初始化、指定处理函数、发送请求的函数
	//开始初始化XMLHttpRequest对象
	if(window.XMLHttpRequest)
	{
		//Mozilla 浏览器
		xmlHttp = new XMLHttpRequest();
		if (xmlHttp.overrideMimeType)
		{
			//设置MiME类别
			xmlHttp.overrideMimeType('text/xml');
		}
	}
	else if (window.ActiveXObject)
	{
		// IE浏览器
		try
		{
			xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
		}
		catch (e)
		{
			try
			{
				xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
			}
			catch (e)
			{
			}
		}
	}
	if (!xmlHttp)
	{
		// 异常，创建对象实例失败
		window.alert("不能创建XMLHttpRequest对象实例.");
		return false;
	}
}






function setOption()
{
	createXMLHttpRequest();
	
	var url	= "?/product/ajax";

	var bigCatSelected = document.search_form.big_cat.value;
	url		= url + "-bid-" + escape(bigCatSelected) +".html";

	document.search_form.small_cat['options'].length = 0;
	document.search_form.small_cat['options'].add(new Option( "小类读取中", "" ));

	document.search_form.small_cat['options'][0].style.color = "#FF0000";

	xmlHttp.open( "GET", url, true );
	xmlHttp.onreadystatechange = searchCallBack;
	xmlHttp.send(null);
}


function searchCallBack()
{
	if (xmlHttp.readyState == 4)
	{
		// 判断对象状态
		if (xmlHttp.status == 200)
		{
			// 信息已经成功返回，开始处理信息
			setSmallCat();
		}
		else
		{
			//页面不正常
			alert(xmlHttp.status+"您所请求的页面有异常。");
		}
	}
}


function setSmallCat()
{
	document.search_form.small_cat.disabled = false;
	document.search_form.small_cat['options'].length = 0;
	document.search_form.small_cat['options'].add(new Option( "请选择小类", "" ));

	var response	= xmlHttp.responseText;
	var arr			= new Array();
	arr				= response.split("|");

	for(var i=1; i<arr.length; i++)
	{
		var arr_tmp	= arr[i].split(",");
		document.getElementById("small_cat").options[i] = new Option(arr_tmp[1], arr_tmp[0]);
	}
}