一个ajax类

var xmlHttp;

var state;

function createXMLHttpRequest() {

if(window.ActiveXObject) {
	
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");

} else if(window.XMLHttpRequest) {

xmlHttp = new XMLHttpRequest();

}

return xmlHttp;

}

function $(id){

return document.getElementById(id);

}

function addOption(id,_json){


var _s = $(id);

_s.options.length = 1;

for(var i=0;i<_json.length; i++){

var option=new Option(_json[i].name,_json[i].value);

_s.add(option);

}

}

function getSelectOption(url,value,id){
//alert("url--->"+url);
//alert("value--->"+value);
//alert("id--->"+id);
state = id;

getValue(url,value);

}

function getValue(url,value){

xmlHttp = createXMLHttpRequest();

xmlHttp.open("post",url,true);

xmlHttp.setRequestHeader('Content-Type','application/x-www-form-urlencoded;charset=GBK');

xmlHttp.onreadystatechange = handleStateChange;

xmlHttp.send("value="+value);

}

function handleStateChange(){

if(xmlHttp.readystate==4){

if(xmlHttp.status==200){

callBack();

}

}

}

function callBack(){

var text = xmlHttp.responseText;

var _json = eval(xmlHttp.responseText);

addOption(state,_json);

}





通道
   <select name="destnumber" id="destnunmberid" value="<%=destnumber!=null?destnumber:""%>" onchange="getSelectOption('http://localhost:8080/chan_all_json.jsp?routeid='+document.getElementById('operatorsid').value,this.value,'servicecode')">
      <option value="">请选择通道</option>
         	<option value="82">82</option>
         </select>
业务代码
<select id="servicecode" name="servicecode" value="<%=servicecode!=null?servicecode:""%>">
<option value="" selected>请选择代码</option>
</select>