select下拉框遍历数据库表中数据生成值

jsp页面触发

//渠道下拉框  

function getChanName() {  
var selectNext =$("#chanId");
$.ajax({  
    
                  type: "post",    
                  contentType:"application/json",    
                  url : "getChanName.do",  
                  dataType: 'json',
                  success: function(data){     
                  var data = eval('(' + data + ')');   
                  if(data.length!="" && data.length!=null){
                          var a = 0;
                          selectNext.append("<option value="+a+"selected>请选择</option>");  
                        for ( var i = 0; i < data.length; i++) {
                            var strSelected = "";
                            if(data[i].chan_name){
                                strSelected = "selected";
                            }
                            selectNext.append("<option value='"+data[i].chan_id + "'" + ">"+data[i].chan_name+"</option>");  
                        }
                        
                   }else{  
                               
                  }  
                     },
                  error: function(XMLHttpRequest, textStatus, errorThrown) {
                         alert(XMLHttpRequest.status);
                         alert(XMLHttpRequest.readyState);
                         alert(textStatus);
                           }
});

}

后台遍历返回json