//得到httpRequest请求
function createXMLHttpRequest(){
	var xmlHttpRequest;
	if(window.ActiveXObject){
		xmlHttpRequest=new ActiveXObject("Microsoft.XMLHTTP");
	}else if(window.XMLHttpRequest){
		xmlHttpRequest=new XmlHttpRequest();
	}
	return xmlHttpRequest;
}
//清空下拉列表框选项
function clearSelect(component){       
    while(component.options.length > 0){
    	component.removeChild(component.options[0]);
    }
}