js operation drop-down box

var obj = document.getElementById('city');//找到下拉框  
                obj.options.length = 0;//清空下拉框  
                var dataObj = eval("(" + data + ")");//解析后台传递的数据  
                var html = "";  
                for ( var i = 0; i < dataObj.length; i++) {//循环数据  
                        html += "<option value="+dataObj[i].fyRegionCd+">"  
                        + dataObj[i].regionNmCn + "</option>";      
                }  
                $("#city").append(html);//赋值