fastadmin 列表展示时字段值截取

{field: '字段名', title: __('lang中的语言名'),formatter:function(value,row,index){
                            value=value?value:'';
                            var length=value.length;
                            if(length&&length>7){
                               length=7;
                               return"<span title ='"+value+"'>"+value.substring(0,length)+"...</span>"
                            }
                            return"<span title ='"+value+"'>"+value.substring(0,length)+"</span>"
                            
                        }},