jquery加载json数据

function changeServer(t){
   var obj=document.getElementById('server');  
   obj.options.length=0;
   
   if(t==4){
   obj.options.add(new Option("人间仙境",1));
   }else if(t==10){
   obj.options.add(new Option("双线1区",1));
   }else{
   var ajax = {
  url: "getServerInfoByGameID", data: {sid:t}, type: 'POST', dataType: 'json', cache: false,
  success: function(data, statusText) {
var serverList="";
var serverName="";
var serverID="";
for(var i=0;i<data.length;i++){
serverName=data[i].server_name;
serverID=data[i].id;
obj.options.add(new Option(serverName,serverID));
}

  },
  error: function(httpRequest, statusText, errorThrown) {
  alert('数据请求时发生错误，请稍后"' + errorThrown + '"', '错误提示', 300, 100);
  }
  };
  $.ajax(ajax);
  return false;   
   }
}